Remove concept of "unsupported extensions", clean up test skips

[jakebailey]

Ever since tsgo started acting like tsc, we have not exposed the "unsupported extensions" warning. It's only used for the test runner.

At this point we are actually burning down JS bugs, so I think it's best to restore them to the regular dirs.

While here, clean up some extra skips that were leftover from before we bulk skipped tests that checked removed features.

[Copilot]

Pull Request Overview

This PR removes the concept of "unsupported extensions" from the TypeScript Go port and cleans up related test skipping logic. The changes simplify the codebase by eliminating functionality that was originally used to handle unsupported file extensions but is no longer needed as the port has matured.

Key changes:

• Removed the UnsupportedExtensions() method from the Program struct and all related tracking
• Eliminated test skipping logic based on unsupported extensions and outFile configuration
• Cleaned up baseline generation to remove unsupported extension handling

Reviewed Changes

Copilot reviewed 4 out of 806 changed files in this pull request and generated no comments.

File	Description
internal/compiler/program.go	Removed the UnsupportedExtensions() method that returned tracked unsupported extensions
internal/compiler/fileloader.go	Removed unsupported extensions tracking from file processing logic
internal/testrunner/compiler_runner.go	Removed test skipping for outFile scenarios and unsupported extension baseline handling
internal/testutil/tsbaseline/type_symbol_baseline.go	Removed unsupported extension check for baseline acceptance