Missing `fixAll` code action/code fix

[iisaduan]

source.fixAll.ts is not implemented for editor.codeActionOnSave in VSCode (see #2444 (comment)).

Currently with only the experimental server, code actions look like this:

The corresponding codefix is not also available, and the underlying individual codefixes (unreachable code, incorrectly implemented interface, etc) are also not ported