Add an option to ensure downloaded PDBs are stripped or non-stripped

[DrChat]

Analogous to symchk's PDB options:

• /pa Public and private symbols
• /pf Verify that PDBs contain full source information
• /ps Verify that PDBs are stripped
• /pt Verify that PDBs are stripped but contain type information

Notably, symchk does not check PDBs that are already cached. We should diverge and check those PDBs too, and re-download them if they do not comply with the options specified.

Waiting on: getsentry/pdb#143