Ability to set daily cap on log analytics workspaces

It is not currently possible to set the daily cap for a Log Analytics workspace via AzureRM PowerShell.

As you can no longer deploy workspaces in the free tier (which capped at 500MB/day), the PerGB2018 SKU requires a visit to the portal to apply a daily cap that will keep a workspace within its 5GB/month allowance.

This can be automated with an ARM template, though that is a much higher barrier to entry than the [New-AzureRmOperationalInsightsWorkspace](https://docs.microsoft.com/en-us/powershell/module/azurerm.operationalinsights/new-azurermoperationalinsightsworkspace?view=azurermps-6.7.0) cmdlet.

Application Insights exposes this functionality via [Set-AzureRmApplicationInsightsDailyCap](https://docs.microsoft.com/en-us/powershell/module/azurerm.applicationinsights/set-azurermapplicationinsightsdailycap).