Error on ES5, fix skipped tests

[jakebailey]

Largely ports microsoft/TypeScript#63067

This also removes ES3 as a value we even recognize. ES3 is the same as "unset", so in the PR where I bumped the submodule and skipped ES3/ES5 tests, I accidentally skipped all tests without any target set.

Such is the risk of having a valid value that is also the unset value.

[Copilot]

Pull request overview

This PR removes ES3 as a recognized compiler target and adds error handling for ES5, porting changes from TypeScript PR #63067. The main issue addressed is that ES3 was both a valid value and the unset/default value, which caused tests without any target setting to be incorrectly skipped.

Changes:

• Removed ES3 from the valid target options
• Added error diagnostics for ES5 target usage
• Updated test infrastructure to handle unrecognized option values
• Generated new baseline files for previously skipped tests

Reviewed changes

Copilot reviewed 298 out of 355 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
internal/tsoptions/enummaps.go	Removed ES3 entry from targetOptionMap
internal/tsoptions/commandlineoption.go	Removed "es3" from deprecated target options
internal/testutil/harnessutil/harnessutil.go	Added tryGetValueOfOptionString to handle unrecognized values; updated skipUnsupportedCompilerOptions to only skip ES5
internal/core/scripttarget_stringer_generated.go	Removed ES3 from stringer generation
internal/core/compileroptions.go	Removed ScriptTargetES3 constant and updated ES5 deprecation comment
internal/compiler/program.go	Uncommented ES5 validation error
testdata/baselines/reference/*	New baseline files for tests that were previously skipped

[jakebailey]

I have a fix for that skipped test; it's the same thing as #2134 but for functions/constructors. Enums also have the bug.