This commit makes `ProcSyms` constructor takes a `bcc_symbol_option`,
and pass it down to underlying calls to control symboling behavior.
If `nullptr` is passed, `ProcSyms` will use default setting, which is
to use debug file, verify debug file checksum, and only load function symbols.

This commit also makes `bcc_symcache_new` take a `bcc_symbol_option`
parameter and pass it to the underlying `ProcSyms` constructor.