This reverts commit 315cce83.

This reverts commit 1c72ab24.

we keep the LogLevel-enum and the plan is to accept the log level when
calling OutputChannel#appendLine so that
logging is supported there

to avoid breaking live share in Insiders

Finalize the definition link api

- Gives fields more explicit names (target and origin)
- Moves api to vscode.d.ts
- Makes other definition providers (such as type definition provider and implementation provider) also return definition links

Fixes #54101

Fixes #52574