Reland "[clang-tidy] modernize-deprecated-headers check should respect extern "C" blocks""

This partially reverts commit e8cae487.
Changes since that commit:
 - Use `SourceManager::isBeforeInTranslationUnit` instead of the fancy
   decomposed decl logarithmic search.
 - Add a test for including a system header containing a deprecated
   include.
 - Add `REQUIRES: system-linux` clause to the test.

Reviewed By: LegalizeAdulthood, whisperity

Differential Revision: https://reviews.llvm.org/D125209