Fail early on mismatched environments/clouds

[thomas11]

Quoting the code comment: CLI authentication can only use the environment that the CLI is configured for. Fail early if that's not the one from config, to avoid obscure errors about missing subscriptions or endpoints later.

Resolves #3274

Sample shell session:

❯ pulumi config -s gov | rg environ
azure-native:environment  usgovernment

❯ az account show | rg environ
  "environmentName": "AzureCloud",

❯ PATH=$HOME/pulumi/pan/bin:$PATH pulumi up -s gov
Previewing update (gov)

     Type                                     Name              Plan       Info
 +   pulumi:pulumi:Stack                      azn-3268-env-gov  create     3 warnings
     └─ azure-native:resources:ResourceGroup  resourceGroup                1 error

Diagnostics:
  azure-native:resources:ResourceGroup (resourceGroup):
    error: The configured Azure environment 'usgovernment' does not match the determined environment 'public'.
    When authenticating using the Azure CLI, the configured environment needs to match the one shown by 'az account show'.
    You can change environments using 'az cloud set --name <environment>'.

[github-actions]

Does the PR have any schema changes?

Looking good! No breaking changes found.
No new resources/functions.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 6 lines in your changes are missing coverage. Please review.

Project coverage is 55.33%. Comparing base (9901424) to head (7ad04f6).
Report is 1 commits behind head on master.

Files	Patch %	Lines
provider/pkg/provider/auth.go	0.00%	5 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3281      +/-   ##
==========================================
- Coverage   55.37%   55.33%   -0.04%     
==========================================
  Files          66       66              
  Lines        9924     9930       +6     
==========================================
  Hits         5495     5495              
- Misses       3996     4001       +5     
- Partials      433      434       +1     

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[mikhailshilkov]

I'm missing a test to go with this change.

[thomas11]

I'm missing a test to go with this change.

Fair enough. The whole area isn't covered much.

#3285 adds a bunch.