Add src_to_binary_ext that returns addrs_syms

[ameeuw]

This PR adds a src_to_binary_ext function that assembles the binary, collects the addresses of symbols, and returns them.
It also alters the existing src_to_binary function to use it in order to print the addresses of symbols out and only return the binary.

This change was necessary, as I had the requirement to know the addresses of symbols to replace them in resulting code segments, and I think it makes sense to not just print the symbols out but to have them available programatically.

Please let me know if there is any further guideline I should follow to get this PR merged - happy to adjust and collaborate.

[ThomasWaldmann]

Thanks for the PR, it makes a lot of sense! :-)

Just one minor nitpick: can you please keep the 2 empty lines between toplevel functions?

Looks like we don't have the pep8 style checker active in the CI here, but we try to follow it nevertheless.

Other than that: LGTM!

[ameeuw]

Thanks for the PR, it makes a lot of sense! :-)

Just one minor nitpick: can you please keep the 2 empty lines between toplevel functions?

Looks like we don't have the pep8 style checker active in the CI here, but we try to follow it nevertheless.

Other than that: LGTM!

Thank you - done.