Automation/script to smoke test existing and new validation logic

[radeksimko]

Context

After introducing enhanced validation in #1368 we have received a number of bug reports about false diagnostics:

• fix: Work around 'unreliable' input data for Registry modules #1456
• Resolve version correctly for backend schema #1453
• decoder: allow objects in for_each hcl-lang#333
• fix output block precondition in 1.2 schema terraform-schema#282
• schema: Fix schema merging for terraform_remote_state data source terraform-schema#272
• schema: Make cloud organization optional terraform-schema#271
• (fix) decoder: Ensure empty objects & tuples still get collected as targets hcl-lang#330
• schema: Declare DefaultValue for relevant attributes terraform-schema#270
• schema: Introduce v1.3 proxy related fields for provisioner connection terraform-schema#269
• fix: Ensure target_platform is recognised in nested connection block terraform-schema#268

and some more continue to trickle in:

• config attribute not expected in terraform_remote_state data source vscode-terraform#1606
• Variable references are not recognised in depends_on vscode-terraform#1598
• provider block for github shows as invalid for an empty app_auth block vscode-terraform#1597
• Incorrectly flagging nested dynamic blocks as errors vscode-terraform#1594
• Variable with empty list causes "No declaration found" on submodules vscode-terraform#1592

Proposal

Instead of letting our users discover and report such cases of false diagnostics we can be more proactive and run our validation logic against publicly available repositories of Terraform code on GitHub, to perform a form of smoke testing of the validation logic.

This can in turn provide us with higher confidence in the validation logic and the schema, and detect at least some, if not most, of the bugs before they even reach users.

• Identify some popular repositories with Terraform code on GitHub and the Terraform Registry
• Create a script (Go code) which can run all existing validation logic
  • Context-less validation (SchemaModuleValidation, SchemaVariablesValidation)
  • Context-dependent validation (ReferenceValidation)
• Run script against those repositories