add support for array splat completion in type syntax and enhance completion context

[polatengin]

Fixes #17610

Design Proposal

When using the resourceInput<> type accessor with chained property access involving arrays, intellisense does not offer * (splat) completion inside square brackets. For example:

param foo resourceInput<'Microsoft.App/containerApps@2024-03-01'>.properties.template.containers[|]

At te cursor position |, no completion is offered for * to access the array item type.

When parsing foo.items[] in a type context, the Bicep parser creates an ArrayTypeSyntax node (interpreting [] as "array of foo.items"), not a TypeArrayAccessSyntax node. The existing completion logic only detected TypeArrayAccessSyntax, which is created when there's already content inside the brackets (like foo[0]).

In this PR we extend the completian context detection to also recognize ArrayTypeSyntax as a valid context for offering the * completion when the cursor is positioned between [ and ].

I added some integration tests to cover;

• Basic array splat completion in type clauses
• Chained typ completions for *.properties.tags.* and *.properties.template.containers[*].probes patterns
• Real resource types, such as; Microsoft.App/containerApps and Microsoft.Resources/tags

Checklist

• I have read and adhere to the contribution guide.

Microsoft Reviewers: Open in CodeFlow

[github-actions]

Test this change out locally with the following install scripts (Action run 21601528735)

VSCode

• Mac/Linux

  bash <(curl -Ls https://aka.ms/bicep/nightly-vsix.sh) --run-id 21601528735

• Windows

  iex "& { $(irm https://aka.ms/bicep/nightly-vsix.ps1) } -RunId 21601528735"

Azure CLI

• Mac/Linux

  bash <(curl -Ls https://aka.ms/bicep/nightly-cli.sh) --run-id 21601528735

• Windows

  iex "& { $(irm https://aka.ms/bicep/nightly-cli.ps1) } -RunId 21601528735"