Support @deprecated on namespace aliases (ImportEqualsDeclaration)

[thromel]

Fixes #62340

Problem

When using @deprecated on a namespace alias like:

export namespace JSX {
    /** @deprecated */
    export import Bar = example.Bar;
}

Accessing JSX.Bar as a type did not show a deprecation warning, even though the alias itself is marked as deprecated.

Root Cause

In checkTypeReferenceOrImport, the resolvedSymbol is the resolved target of the alias (e.g., example.Bar), not the alias symbol itself. Since the alias (the ImportEqualsDeclaration) was not being checked, its @deprecated JSDoc was ignored.

Fix

Added code to also resolve the entity name without resolving aliases (dontResolveAlias: true) and check if the alias symbol itself is deprecated using isDeprecatedSymbol().

Test

Added tests/cases/fourslash/jsdocDeprecated_namespaceAlias.ts covering:

1. Direct type alias with @deprecated (already worked)
2. ImportEqualsDeclaration with @deprecated (the bug being fixed)
3. ImportEqualsDeclaration aliasing a deprecated type (already worked)

[typescript-bot]

With 6.0 out as the final release vehicle for this codebase, we're closing all PRs that don't fit the merge criteria for post-6.0 patches. If you think this was a mistake and this PR fits the post-6.0 patch criteria, please post to the 6.0 iteration issue with details (specifically, which PR and which patch criteria it satisfies).

Next steps for PRs:

• For crash bugfixes or language service improvements, PRs are currently accepted at the typescript-go repo
• Changes to type system behavior should wait until after 7.0, at which point mainline TypeScript development will resume in this repository with the Go codebase
• Library file updates (lib.d.ts etc) continue to live in this repo or the DOM Generator repo as appropriate