Save compilation warnings

[montyly]

Currently the compilation warnings are not saved by crytic-compile, and they are just being emitted through log:

https://github.com/crytic/crytic-compile/blob/35d95d6cb7716290ff4bf21ba9dcc8e582c6ee04/crytic_compile/platform/solc.py#L534-L541

https://github.com/crytic/crytic-compile/blob/35d95d6cb7716290ff4bf21ba9dcc8e582c6ee04/crytic_compile/platform/truffle.py#L178-L189

etc..

We could save the log, and make them available for third parties analyses. We need to check what errors are reported by every tool (stdout/stderr).

This will require to update our standard export to load/save the new info: https://github.com/crytic/crytic-compile/blob/master/crytic_compile/platform/standard.py