Use more abseil components

[shinh]

Now that we have third_party/abseil and I think we should start using it especially from compiler directory (where we don't need to care about the binary size)

• debugging: stacktrace and symbolize
• strings: str_cat, etc.
• types/variant: should be used from other union like classes such as Type
• types/optional: I think we should NOT use it for now to be consistent with ChainerX