fix: allow enum member references with non-identifier names as computed property names

[cyphercodes]

Fixes #25083

Previously, using an enum member with a non-identifier name (like '3x14') as a computed property name in a type literal would incorrectly produce an error:
'A computed property name in a type literal must refer to an expression whose type is a literal type or a unique symbol type.'

The fix updates checkGrammarForInvalidDynamicName to also allow element access expressions where:

1. The argument expression is a string or number literal
2. The expression being accessed is an entity name expression (like Type in Type['3x14'])

This enables patterns like:

enum Type { '3x14' = '3x14' }
type TypeMap = { [Type['3x14']]: any }  // Now works!

Test case included.

[jakebailey]

Sorry, but we are not accepting PRs of this kind at this time. https://github.com/microsoft/TypeScript#:~:text=NOTE%3A%20Code%20changes%20in%20this%20repo%20are%20now%20limited%20to%20a%20small%20category%20of%20fixes%3A

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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
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