Change get_global_offset_from_line to also take an optional character position

[Xenomega]

Currently, crytic-compile has a function to take a source file offset and convert it into line and character position numbers. To reverse this operation, get_global_offset_from_line could be used, but it only takes a line number, not a character position number.

This PR adds an optional character position parameter which can be used to specify a position on a line number which we want to obtain a source offset for.

It also renames get_global_offset_from_line to get_global_offset_from_line_and_character and get_line_from_offset into get_line_and_character_from_offset for clarity.

[bohendo]

I assume the get_line_and_character_from_offset and get_global_offset_from_line_and_character functions are only intended to be used by dependent python packages (e.g. slither) and not by crytic-compile itself? If so, this looks good to me.

[montyly]

This PR has been on hold because the breaking change might impact other projects. Slither has an open PR crytic/slither#889, but the related code has changed so it needs to be updated

Before merging this, we should check in the crytic and trailofbits orgs if other projects are affected (manticore or evm-cfg-builder maybe?)