WebApp:Get-AzWebApp fails on resourceGroups with a single char name

## Description

Trying to run Get-AzWebApp on a resource group with single char name fails with:

Get-AzWebApp: 'resourceGroupName' does not match expected pattern '^[-\w\._\(\)]+[^\.]$'.

## Steps to reproduce

```powershell

New-AzResourceGroup -Name A -Location westus2
Get-AzWebApp -ResourceGroupName A

```

## Environment data
```
Name Value
---- -----
PSVersion 7.1.1
PSEdition Core
GitCommitId 7.1.1
OS Microsoft Windows 10.0.19042
Platform Win32NT
PSCompatibleVersions {1.0, 2.0, 3.0, 4.0…}
PSRemotingProtocolVersion 2.3
SerializationVersion 1.1.0.1
WSManStackVersion 3.0
```

## Module versions

```powershell
ModuleType Version PreRelease Name PSEdition ExportedCommands
---------- ------- ---------- ---- --------- ----------------
Script 5.4.0 Az Core,Desk
Script 2.2.4 Az.Accounts Core,Desk {Disable-AzDataCollection, Disable-AzContextAutosave, Enable-AzDataCollection, Enable-AzContextAutosave…}
Script 1.1.1 Az.Advisor Core,Desk {Get-AzAdvisorRecommendation, Enable-AzAdvisorRecommendation, Disable-AzAdvisorRecommendation, Get-AzAdvisor…
Script 2.0.1 Az.Aks Core,Desk {Get-AzAksCluster, New-AzAksCluster, Remove-AzAksCluster, Import-AzAksCredential…}
Script 1.1.4 Az.AnalysisServices Core,Desk {Resume-AzAnalysisServicesServer, Suspend-AzAnalysisServicesServer, Get-AzAnalysisServicesServer, Remove-AzA…
Script 2.2.0 Az.ApiManagement Core,Desk {Add-AzApiManagementApiToGateway, Add-AzApiManagementApiToProduct, Add-AzApiManagementProductToGroup, Add-Az…
Script 1.0.0 Az.AppConfiguration Core,Desk {Get-AzAppConfigurationStore, Get-AzAppConfigurationStoreKey, New-AzAppConfigurationStore, New-AzAppConfigur…
Script 1.1.0 Az.ApplicationInsights Core,Desk {Get-AzApplicationInsights, New-AzApplicationInsights, Remove-AzApplicationInsights, Update-AzApplicationIns…
Script 1.4.2 Az.Automation Core,Desk {Get-AzAutomationHybridWorkerGroup, Remove-AzAutomationHybridWorkerGroup, Get-AzAutomationJobOutputRecord, I…
Script 3.1.0 Az.Batch Core,Desk {Remove-AzBatchAccount, Get-AzBatchAccount, Get-AzBatchAccountKey, New-AzBatchAccount…}
Script 2.0.0 Az.Billing Core,Desk {Get-AzBillingInvoice, Get-AzBillingPeriod, Get-AzEnrollmentAccount, Get-AzConsumptionBudget…}
Script 1.6.0 Az.Cdn Core,Desk {Get-AzCdnProfile, Get-AzCdnProfileSsoUrl, New-AzCdnProfile, Remove-AzCdnProfile…}
Script 1.8.0 Az.CognitiveServices Core,Desk {Get-AzCognitiveServicesAccount, Get-AzCognitiveServicesAccountKey, Get-AzCognitiveServicesAccountSku, Get-A…
Script 4.8.0 Az.Compute Core,Desk {Remove-AzAvailabilitySet, Get-AzAvailabilitySet, New-AzAvailabilitySet, Update-AzAvailabilitySet…}
Script 1.0.3 Az.ContainerInstance Core,Desk {New-AzContainerGroup, Get-AzContainerGroup, Remove-AzContainerGroup, Get-AzContainerInstanceLog}
Script 2.1.0 Az.ContainerRegistry Core,Desk {New-AzContainerRegistry, Get-AzContainerRegistry, Update-AzContainerRegistry, Remove-AzContainerRegistry…}
Script 1.0.0 Az.CosmosDB Core,Desk {Get-AzCosmosDBSqlContainer, Get-AzCosmosDBSqlContainerThroughput, Get-AzCosmosDBSqlDatabase, Get-AzCosmosDB…
Script 1.1.0 Az.DataBoxEdge Core,Desk {Get-AzDataBoxEdgeJob, Get-AzDataBoxEdgeDevice, Invoke-AzDataBoxEdgeDevice, New-AzDataBoxEdgeDevice…}
Script 1.0.2 Az.Databricks Core,Desk {Get-AzDatabricksVNetPeering, Get-AzDatabricksWorkspace, New-AzDatabricksVNetPeering, New-AzDatabricksWorksp…
Script 1.11.3 Az.DataFactory Core,Desk {Set-AzDataFactoryV2, Update-AzDataFactoryV2, Get-AzDataFactoryV2, Remove-AzDataFactoryV2…}
Script 1.0.2 Az.DataLakeAnalytics Core,Desk {Get-AzDataLakeAnalyticsDataSource, New-AzDataLakeAnalyticsCatalogCredential, Remove-AzDataLakeAnalyticsCata…
Script 1.3.0 Az.DataLakeStore Core,Desk {Get-AzDataLakeStoreTrustedIdProvider, Remove-AzDataLakeStoreTrustedIdProvider, Remove-AzDataLakeStoreFirewa…
Script 1.0.0 Az.DataShare Core,Desk {New-AzDataShareAccount, Get-AzDataShareAccount, Remove-AzDataShareAccount, New-AzDataShare…}
Script 1.1.0 Az.DeploymentManager Core,Desk {Get-AzDeploymentManagerArtifactSource, New-AzDeploymentManagerArtifactSource, Set-AzDeploymentManagerArtifa…
Script 2.1.1 Az.DesktopVirtualization Core,Desk {Disconnect-AzWvdUserSession, Expand-AzWvdMsixImage, Get-AzWvdApplication, Get-AzWvdApplicationGroup…}
Script 1.0.2 Az.DevTestLabs Core,Desk {Get-AzDtlAllowedVMSizesPolicy, Get-AzDtlAutoShutdownPolicy, Get-AzDtlAutoStartPolicy, Get-AzDtlVMsPerLabPol…
Script 1.1.2 Az.Dns Core,Desk {Get-AzDnsRecordSet, New-AzDnsRecordConfig, Remove-AzDnsRecordSet, Set-AzDnsRecordSet…}
Script 1.3.0 Az.EventGrid Core,Desk {New-AzEventGridTopic, Get-AzEventGridTopic, Set-AzEventGridTopic, New-AzEventGridTopicKey…}
Script 1.7.1 Az.EventHub Core,Desk {New-AzEventHubNamespace, Get-AzEventHubNamespace, Set-AzEventHubNamespace, Remove-AzEventHubNamespace…}
Script 1.6.1 Az.FrontDoor Core,Desk {New-AzFrontDoor, Get-AzFrontDoor, Set-AzFrontDoor, Remove-AzFrontDoor…}
Script 2.0.0 Az.Functions Core,Desk {Get-AzFunctionApp, Get-AzFunctionAppAvailableLocation, Get-AzFunctionAppPlan, Get-AzFunctionAppSetting…}
Script 4.1.1 Az.HDInsight Core,Desk {Get-AzHDInsightJob, New-AzHDInsightSqoopJobDefinition, Wait-AzHDInsightJob, New-AzHDInsightStreamingMapRedu…
Script 1.2.0 Az.HealthcareApis Core,Desk {New-AzHealthcareApisService, Remove-AzHealthcareApisService, Set-AzHealthcareApisService, Get-AzHealthcareA…
Script 2.7.2 Az.IotHub Core,Desk {Add-AzIotHubKey, Get-AzIotHubEventHubConsumerGroup, Get-AzIotHubConnectionString, Get-AzIotHubJob…}
Script 3.3.1 Az.KeyVault Core,Desk {Add-AzKeyVaultCertificate, Update-AzKeyVaultCertificate, Stop-AzKeyVaultCertificateOperation, Get-AzKeyVaul…
Script 1.0.1 Az.Kusto Core,Desk {Add-AzKustoClusterLanguageExtension, Add-AzKustoDatabasePrincipal, Get-AzKustoAttachedDatabaseConfiguration…
Script 1.5.0 Az.LogicApp Core,Desk {Get-AzIntegrationAccountAgreement, Get-AzIntegrationAccountAssembly, Get-AzIntegrationAccountBatchConfigura…
Script 1.1.3 Az.MachineLearning Core,Desk {Move-AzMlCommitmentAssociation, Get-AzMlCommitmentAssociation, Get-AzMlCommitmentPlanUsageHistory, Remove-A…
Script 1.1.0 Az.Maintenance Core,Desk {Get-AzApplyUpdate, Get-AzConfigurationAssignment, Get-AzMaintenanceConfiguration, Get-AzMaintenanceUpdate…}
Script 2.0.0 Az.ManagedServices Core,Desk {Get-AzManagedServicesAssignment, New-AzManagedServicesAssignment, Remove-AzManagedServicesAssignment, Get-A…
Script 1.0.2 Az.MarketplaceOrdering Core,Desk {Get-AzMarketplaceTerms, Set-AzMarketplaceTerms}
Script 1.1.1 Az.Media Core,Desk {Sync-AzMediaServiceStorageKey, Set-AzMediaServiceKey, Get-AzMediaServiceKey, Get-AzMediaServiceNameAvailabi…
Script 2.4.0 Az.Monitor Core,Desk {Get-AzMetricDefinition, Get-AzMetric, Remove-AzLogProfile, Get-AzLogProfile…}
Script 4.5.0 Az.Network Core,Desk {Add-AzApplicationGatewayAuthenticationCertificate, Get-AzApplicationGatewayAuthenticationCertificate, New-A…
Script 1.1.1 Az.NotificationHubs Core,Desk {Get-AzNotificationHub, Get-AzNotificationHubAuthorizationRule, Get-AzNotificationHubListKey, Get-AzNotifica…
Script 2.3.0 Az.OperationalInsights Core,Desk {New-AzOperationalInsightsAzureActivityLogDataSource, New-AzOperationalInsightsCustomLogDataSource, Disable-…
Script 1.4.0 Az.PolicyInsights Core,Desk {Get-AzPolicyEvent, Get-AzPolicyState, Get-AzPolicyStateSummary, Get-AzPolicyRemediation…}
Script 1.1.2 Az.PowerBIEmbedded Core,Desk {Remove-AzPowerBIWorkspaceCollection, Get-AzPowerBIWorkspaceCollection, Get-AzPowerBIWorkspaceCollectionAcce…
Script 1.0.3 Az.PrivateDns Core,Desk {Get-AzPrivateDnsZone, Remove-AzPrivateDnsZone, Set-AzPrivateDnsZone, New-AzPrivateDnsZone…}
Script 3.3.0 Az.RecoveryServices Core,Desk {Get-AzRecoveryServicesBackupProperty, Get-AzRecoveryServicesVault, Get-AzRecoveryServicesVaultSettingsFile,…
Script 1.4.0 Az.RedisCache Core,Desk {Remove-AzRedisCachePatchSchedule, New-AzRedisCacheScheduleEntry, Get-AzRedisCachePatchSchedule, New-AzRedis…
Script 1.0.3 Az.Relay Core,Desk {New-AzRelayNamespace, Get-AzRelayNamespace, Set-AzRelayNamespace, Remove-AzRelayNamespace…}
Script 3.2.0 Az.Resources Core,Desk {Get-AzProviderOperation, Remove-AzRoleAssignment, Get-AzRoleAssignment, New-AzRoleAssignment…}
Script 1.4.1 Az.ServiceBus Core,Desk {New-AzServiceBusNamespace, Get-AzServiceBusNamespace, Set-AzServiceBusNamespace, Remove-AzServiceBusNamespa…
Script 2.2.2 Az.ServiceFabric Core,Desk {Add-AzServiceFabricClientCertificate, Add-AzServiceFabricClusterCertificate, Add-AzServiceFabricNode, Add-A…
Script 1.2.0 Az.SignalR Core,Desk {New-AzSignalR, Get-AzSignalR, Get-AzSignalRKey, New-AzSignalRKey…}
Script 2.15.0 Az.Sql Core,Desk {Get-AzSqlDatabaseTransparentDataEncryption, Get-AzSqlDatabaseTransparentDataEncryptionActivity, Set-AzSqlDa…
Script 1.1.0 Az.SqlVirtualMachine Core,Desk {New-AzSqlVM, Get-AzSqlVM, Update-AzSqlVM, Remove-AzSqlVM…}
Script 3.2.1 Az.Storage Core,Desk {Get-AzStorageAccount, Get-AzStorageAccountKey, New-AzStorageAccount, New-AzStorageAccountKey…}
Script 1.4.0 Az.StorageSync Core,Desk {Invoke-AzStorageSyncCompatibilityCheck, New-AzStorageSyncService, Get-AzStorageSyncService, Set-AzStorageSy…
Script 1.0.1 Az.StreamAnalytics Core,Desk {Get-AzStreamAnalyticsFunction, Get-AzStreamAnalyticsDefaultFunctionDefinition, New-AzStreamAnalyticsFunctio…
Script 1.0.0 Az.Support Core,Desk {Get-AzSupportService, Get-AzSupportProblemClassification, Get-AzSupportTicket, Get-AzSupportTicketCommunica…
Script 1.0.4 Az.TrafficManager Core,Desk {Add-AzTrafficManagerCustomHeaderToEndpoint, Remove-AzTrafficManagerCustomHeaderFromEndpoint, Add-AzTrafficM…
Script 2.2.0 Az.Websites Core,Desk {Get-AzAppServicePlan, Set-AzAppServicePlan, New-AzAppServicePlan, Remove-AzAppServicePlan…}
Manifest 2.0.3 AzTable Desk {Add-AzTableRow, Get-AzTableRow, Get-AzTableRowAll, Get-AzTableRowByPartitionKeyRowKey…}

```

Note that if there are no webapps in the subscription, simply running Get-AzWebApp and having a resourceGroup in the sub with a single char name returns the same error (which is much harder to debug).