This subsumes most of the params to ClangdServer and ClangdLSPServer.
Adjacent changes:
- tests use a consistent set of options, except when testing specific options
- tests that previously used synchronous mode for convenience no longer do
- added a runAddDocument helper to SyncAPIs to mitigate the extra code
- rearranged main a bit to follow the structure of the options
Shouldn't this be better implemented as a utility function in tests?
Also what is the purpose of making global function in header file static?