Better error message when IdP cannot be found

If a customer attempts to run `create-team` with an IdP group set, but their GitHub org is not EMU-enabled, or that specific group doesn't exist in the IdP, the CLI will crash with an unhelpful error message (in non-verbose mode it will just be our generic "An error has occurred").

We should give a more useful error message, letting the user know that they shouldn't be trying to link to IdP groups in non-EMU orgs, or that their specified IdP group can't be found.

```
[11:45 AM] [DEBUG] HTTP GET: https://raw.githubusercontent.com/github/gh-gei/main/LATEST-VERSION.txt
[11:45 AM] [DEBUG] RESPONSE (OK): v0.26

[11:45 AM] [INFO] You are running the latest version of the ado2gh CLI [v0.26]
[11:45 AM] [INFO] Creating GitHub team...
[11:45 AM] [INFO] GITHUB ORG: mickey-test-migrations
[11:45 AM] [INFO] TEAM NAME: MyShuttle-Maintainers
[11:45 AM] [INFO] IDP GROUP: MyShuttle-Maintainers
[11:45 AM] [DEBUG] HTTP GET: https://api.github.com/orgs/mickey-test-migrations/teams
[11:45 AM] [DEBUG] GITHUB REQUEST ID: E4DB:5466:CB8CF8:19F859B:6329EE41
[11:45 AM] [DEBUG] RESPONSE (OK): [{"name":"MyShuttle-Maintainers","id":6656283,"node_id":"T_kwDOBsS6Ms4AZZEb","slug":"myshuttle-maintainers","description":null,"privacy":"closed","url":"https://api.github.com/organizations/113556018/team/6656283","html_url":"https://github.com/orgs/mickey-test-migrations/teams/myshuttle-maintainers","members_url":"https://api.github.com/organizations/113556018/team/6656283/members{/member}","repositories_url":"https://api.github.com/organizations/113556018/team/6656283/repos","permission":"pull","parent":null}]
[11:45 AM] [INFO] Team 'MyShuttle-Maintainers' already exists - New team will not be created
[11:45 AM] [DEBUG] HTTP GET: https://api.github.com/orgs/mickey-test-migrations/teams
[11:45 AM] [DEBUG] GITHUB REQUEST ID: E4DB:5466:CB8D50:19F864F:6329EE41
[11:45 AM] [DEBUG] RESPONSE (OK): [{"name":"MyShuttle-Maintainers","id":6656283,"node_id":"T_kwDOBsS6Ms4AZZEb","slug":"myshuttle-maintainers","description":null,"privacy":"closed","url":"https://api.github.com/organizations/113556018/team/6656283","html_url":"https://github.com/orgs/mickey-test-migrations/teams/myshuttle-maintainers","members_url":"https://api.github.com/organizations/113556018/team/6656283/members{/member}","repositories_url":"https://api.github.com/organizations/113556018/team/6656283/repos","permission":"pull","parent":null}]
[11:45 AM] [DEBUG] HTTP GET: https://api.github.com/orgs/mickey-test-migrations/teams/myshuttle-maintainers/members?per_page=100
[11:45 AM] [DEBUG] GITHUB REQUEST ID: E4DB:5466:CB8D83:19F86AF:6329EE41
[11:45 AM] [DEBUG] RESPONSE (OK): [{"login":"mickeygousset","id":20031479,"node_id":"MDQ6VXNlcjIwMDMxNDc5","avatar_url":"https://avatars.githubusercontent.com/u/20031479?v=4","gravatar_id":"","url":"https://api.github.com/users/mickeygousset","html_url":"https://github.com/mickeygousset","followers_url":"https://api.github.com/users/mickeygousset/followers","following_url":"https://api.github.com/users/mickeygousset/following{/other_user}","gists_url":"https://api.github.com/users/mickeygousset/gists{/gist_id}","starred_url":"https://api.github.com/users/mickeygousset/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/mickeygousset/subscriptions","organizations_url":"https://api.github.com/users/mickeygousset/orgs","repos_url":"https://api.github.com/users/mickeygousset/repos","events_url":"https://api.github.com/users/mickeygousset/events{/privacy}","received_events_url":"https://api.github.com/users/mickeygousset/received_events","type":"User","site_admin":true}]
[11:45 AM] [DEBUG] HTTP DELETE: https://api.github.com/orgs/mickey-test-migrations/teams/myshuttle-maintainers/memberships/mickeygousset
[11:45 AM] [DEBUG] GITHUB REQUEST ID: E4DB:5466:CB8DCE:19F8752:6329EE41
[11:45 AM] [DEBUG] RESPONSE (NoContent):
[11:45 AM] [DEBUG] HTTP GET: https://api.github.com/orgs/mickey-test-migrations/external-groups
[11:45 AM] [DEBUG] GITHUB REQUEST ID: E4DB:5466:CB8E3B:19F884A:6329EE42
[11:45 AM] [DEBUG] RESPONSE (BadRequest): {"message":"This organization is not part of externally managed enterprise.","documentation_url":"https://docs.github.com/rest/reference/teams#list-external-idp-groups-for-an-organization"}
[11:45 AM] [DEBUG] Call failed with HTTP BadRequest, retrying...
[11:45 AM] [DEBUG] HTTP GET: https://api.github.com/orgs/mickey-test-migrations/external-groups
[11:45 AM] [DEBUG] GITHUB REQUEST ID: E4DB:5466:CB8FE3:19F8B94:6329EE43
[11:45 AM] [DEBUG] RESPONSE (BadRequest): {"message":"This organization is not part of externally managed enterprise.","documentation_url":"https://docs.github.com/rest/reference/teams#list-external-idp-groups-for-an-organization"}
[11:45 AM] [DEBUG] Call failed with HTTP BadRequest, retrying...
[11:45 AM] [DEBUG] HTTP GET: https://api.github.com/orgs/mickey-test-migrations/external-groups
[11:45 AM] [DEBUG] GITHUB REQUEST ID: E4DB:5466:CB92F0:19F91B9:6329EE45
[11:45 AM] [DEBUG] RESPONSE (BadRequest): {"message":"This organization is not part of externally managed enterprise.","documentation_url":"https://docs.github.com/rest/reference/teams#list-external-idp-groups-for-an-organization"}
[11:45 AM] [DEBUG] Call failed with HTTP BadRequest, retrying...
[11:46 AM] [DEBUG] HTTP GET: https://api.github.com/orgs/mickey-test-migrations/external-groups
[11:46 AM] [DEBUG] GITHUB REQUEST ID: E4DB:5466:CB97B4:19F9B88:6329EE48
[11:46 AM] [DEBUG] RESPONSE (BadRequest): {"message":"This organization is not part of externally managed enterprise.","documentation_url":"https://docs.github.com/rest/reference/teams#list-external-idp-groups-for-an-organization"}
[11:46 AM] [DEBUG] Call failed with HTTP BadRequest, retrying...
[11:46 AM] [DEBUG] HTTP GET: https://api.github.com/orgs/mickey-test-migrations/external-groups
[11:46 AM] [DEBUG] GITHUB REQUEST ID: E4DB:5466:CB9F7D:19FAB49:6329EE4C
[11:46 AM] [DEBUG] RESPONSE (BadRequest): {"message":"This organization is not part of externally managed enterprise.","documentation_url":"https://docs.github.com/rest/reference/teams#list-external-idp-groups-for-an-organization"}
[11:46 AM] [DEBUG] Call failed with HTTP BadRequest, retrying...
[11:46 AM] [DEBUG] HTTP GET: https://api.github.com/orgs/mickey-test-migrations/external-groups
[11:46 AM] [DEBUG] GITHUB REQUEST ID: E4DB:5466:CBA83D:19FBD16:6329EE51
[11:46 AM] [DEBUG] RESPONSE (BadRequest): {"message":"This organization is not part of externally managed enterprise.","documentation_url":"https://docs.github.com/rest/reference/teams#list-external-idp-groups-for-an-organization"}
[11:46 AM] [ERROR] System.Net.Http.HttpRequestException: Response status code does not indicate success: 400 (Bad Request).
at System.Net.Http.HttpResponseMessage.EnsureSuccessStatusCode()
at OctoshiftCLI.GithubClient.SendAsync(HttpMethod httpMethod, String url, Object body, HttpStatusCode status, Dictionary`2 customHeaders)
at OctoshiftCLI.GithubClient.<>c__DisplayClass5_0.<b__0>d.MoveNext()
--- End of stack trace from previous location ---
at Polly.Retry.AsyncRetryEngine.ImplementationAsync[TResult](Func`3 action, Context context, CancellationToken cancellationToken, ExceptionPredicates shouldRetryExceptionPredicates, ResultPredicates`1 shouldRetryResultPredicates, Func`5 onRetryAsync, Int32 permittedRetryCount, IEnumerable`1 sleepDurationsEnumerable, Func`4 sleepDurationProvider, Boolean continueOnCapturedContext)
at Polly.AsyncPolicy.ExecuteAsync[TResult](Func`3 action, Context context, CancellationToken cancellationToken, Boolean continueOnCapturedContext)
at OctoshiftCLI.RetryPolicy.HttpRetry[T](Func`1 func, Func`2 filter)
at OctoshiftCLI.GithubClient.GetAsync(String url, Dictionary`2 customHeaders)
at OctoshiftCLI.GithubApi.GetIdpGroupId(String org, String groupName)
at OctoshiftCLI.Commands.CreateTeamCommandBase.Handle(String githubOrg, String teamName, String idpGroup, String githubPat, Boolean verbose)
at System.CommandLine.Invocation.CommandHandler.GetExitCodeAsync(Object value, InvocationContext context)
at System.CommandLine.Invocation.ModelBindingCommandHandler.InvokeAsync(InvocationContext context)
at System.CommandLine.Invocation.InvocationPipeline.<>c__DisplayClass4_0.<b__0>d.MoveNext()
--- End of stack trace from previous location ---
at System.CommandLine.Builder.CommandLineBuilderExtensions.<>c__DisplayClass23_0.<b__0>d.MoveNext()
--- End of stack trace from previous location ---
at System.CommandLine.Builder.CommandLineBuilderExtensions.<>c__DisplayClass16_0.<b__0>d.MoveNext()
--- End of stack trace from previous location ---
at System.CommandLine.Builder.CommandLineBuilderExtensions.<>c__DisplayClass27_0.<b__1>d.MoveNext()
--- End of stack trace from previous location ---
at System.CommandLine.Builder.CommandLineBuilderExtensions.<>c__DisplayClass25_0.<b__0>d.MoveNext()
--- End of stack trace from previous location ---
at System.CommandLine.Builder.CommandLineBuilderExtensions.<>c.<b__24_0>d.MoveNext()
--- End of stack trace from previous location ---
at System.CommandLine.Builder.CommandLineBuilderExtensions.<>c__DisplayClass22_0.<b__0>d.MoveNext()
--- End of stack trace from previous location ---
at System.CommandLine.Builder.CommandLineBuilderExtensions.<>c__DisplayClass11_0.<b__0>d.MoveNext()
--- End of stack trace from previous location ---
at System.CommandLine.Builder.CommandLineBuilderExtensions.<>c.<b__10_0>d.MoveNext()
--- End of stack trace from previous location ---
at System.CommandLine.Builder.CommandLineBuilderExtensions.<>c__DisplayClass14_0.<b__0>d.MoveNext()