[clang] SIGSEGV fix at clang::ASTContext::getRawCommentForDeclNoCacheImpl

The `File` might point to an invalid `FileID` when the AST is broken. That leads to clang/clangd crashes while processing comments. The relevant part of the crash is below
```
 #4 0x00007f1d7fbf95bc std::_Rb_tree<unsigned int, std::pair<unsigned int const, clang::RawComment*>, std::_Select1st<std::pair<unsigned int const, clang::RawComment*>>, std::less<unsigned int>, std::allocator<std::pair<unsigned int const
, clang::RawComment*>>>::_M_lower_bound(std::_Rb_tree_node<std::pair<unsigned int const, clang::RawComment*>> const*, std::_Rb_tree_node_base const*, unsigned int const&) const /usr/include/c++/8/bits/stl_tree.h:1911:2
 #5 0x00007f1d7fbf95bc std::_Rb_tree<unsigned int, std::pair<unsigned int const, clang::RawComment*>, std::_Select1st<std::pair<unsigned int const, clang::RawComment*>>, std::less<unsigned int>, std::allocator<std::pair<unsigned int const, clang::RawComment*>>>::lower_bound(unsigned int const&) const /usr/include/c++/8/bits/stl_tree.h:1214:56
 #6 0x00007f1d7fbf95bc std::map<unsigned int, clang::RawComment*, std::less<unsigned int>, std::allocator<std::pair<unsigned int const, clang::RawComment*>>>::lower_bound(unsigned int const&) const /usr/include/c++/8/bits/stl_map.h:1264:36
 #7 0x00007f1d7fbf95bc clang::ASTContext::getRawCommentForDeclNoCacheImpl(clang::Decl const*, clang::SourceLocation, std::map<unsigned int, clang::RawComment*, std::less<unsigned int>, std::allocator<std::pair<unsigned int const, clang::RawComment*>>> const&) const /home/ivanmurashko/local/llvm-project/clang/lib/AST/ASTContext.cpp:226:57
```

The corresponding LIT test that reproduces the crash was also added

Same issue is described at https://bugs.llvm.org/show_bug.cgi?id=49707

Reviewed By: gribozavr2

Differential Revision: https://reviews.llvm.org/D131675