The language service relies on a "context" file that is used as the
canonical "containing file" when performing module resolution.
This file is unnecessary since the language service host's current
directory always default to the location of tsconfig.json for the
project, which would give the correct result.
This refactoring allows us to simplify the "typescript host" and also
removes the need for custom logic to find tsconfig.json.
PR Close#32015
a91ab15525