[PDB] Do not record PGO or coverage public symbols

These symbols are long, and they tend to cause the PDB file size to
overflow. They are generally not necessary when debugging problems in
user code.

This change reduces the size of chrome.dll.pdb with coverage from
6,937,108,480 bytes to 4,690,210,816 bytes.

Differential Revision: https://reviews.llvm.org/D102719