This commit introduces the template type-checking context API, which manages
inlining of type constructors and type-check blocks into ts.SourceFiles.
This API will be used by ngtsc to generate a type-checking ts.Program.
An TypeCheckProgramHost is provided which can wrap a normal ts.CompilerHost
and intercept getSourceFile() calls. This can be used to provide source
files with type check blocks to a ts.Program for type-checking.
PR Close#26203