[clangd] Propagate main context into ClangdServer
Summary:
Currently clangd initializes the ClangdServer lazily during
onInitialize request, and it results in propagation of caller's context rather
than the main context created ClangdLSPServer.
This patch changes the logic to store main context that created ClangdLSPServer
and pass it onto to ClangdServer and other objects like CDBs.
Reviewers: sammccall
Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, usaxena95, cfe-commits
Tags: #clang
Differential Revision: https://reviews.llvm.org/D68978
llvm-svn: 374892