[clangd] Move the existing heder-source-switch implemenation out of clangdServer.

Summary: This is a NFC change.

Reviewers: kadircet

Reviewed By: kadircet

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D67960

git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@372841 91177308-0d34-0410-b5e6-96231b3b80d8
7 files changed