[compiler] Fix some issues with functions

[witemple-msft]

• Functions were previously not correctly validating that arguments assigned to the rest parameter constraint were compatible with the constraint. This fixes that issue and adds a regression test.
• Function diagnostics were incorrectly targeted in some cases that this change addresses.
• Function type signatures in tspd were rendered a little bit incorrectly and this PR addresses that.
• Function documentation had a few typos that this PR fixes (TypeScript -> TypeSpec, one invalid identifier in an example)

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/@typespec/compiler@10880

npm i https://pkg.pr.new/@typespec/tspd@10880

commit: ca19506

[github-actions]

All changed packages have been documented.

• ✅ @typespec/compiler
• ✅ @typespec/tspd

Show changes

@typespec/compiler - fix ✏️

Validate function rest arguments and report function call argument count diagnostics at call sites.

@typespec/tspd - fix ✏️

Render function type signatures with arrow syntax and avoid internal compiler imports.

[azure-sdk-automation]

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