fix: tsetse checker must be initialized with latest program
fix: tsetse checker must be initialized with latest program

Since ts.Program is an immutable data structure, the tsetse checker
must get hold of a new instance of the ts.Program every time
`getSemanticDiagnostics` is called. There is no way to do this currently,
so just create a new tsetse Checker instance every time.

Closes #506

PiperOrigin-RevId: 330752912

bazelbuild/rules_typescript,bazelbuild/rules_typescript,bazelbuild/rules_typescript