Clean up bcc_exception.h

[palmtenor]

• Remove unused headers and Macros.
• Implement a StatusTuple class that has code() and msg() method, instead of using std::get and std::tuple, as suggested by @4ast and @drarmstr in C++ helper class for BCC #781.
• clang-format -i on the file.

[4ast]

probably makes sense to convert StatusTuple to proper class and add code()/msg() methods.

[palmtenor]

Updated according to comment

[4ast]

since it's in the header file, it probably needs 'static inline' ?

[palmtenor]

Should I rename mkstatus_ in frontends/b/node.h to be mkstatus? I guess originally the underscore is to avoid name conflict with the mkstatus functions from exception.h. But we don't have those anymore...

[4ast]

you could have kept mkstatus() as inline func that returns StatusTuple, but since you've changed all of the callsites anyway, I think it's fine.