fix(configfile): fix bugs, optimize parser, add support for normal an inline comments and add unit tests

[gmmcosta15]

Description

• Feature
• Bug fix
• Code refactor
• Documentation

This pull request intruduces:

• Fix data-corruption bug in _parse_file: separator normalisation was replacing every : and = in a line instead of just the first one, silently mangling URLs, tokens, and section names with colons
• Fix get(), getint(), getfloat(), getboolean() default-handling: missing options with no default now raise NoOptionError instead of returning Sentinel.MISSING; get() no longer passes the fallback through the parser
• Fix add_option(value=None) writing the literal string "None" instead of a value-less option line
• Convert all logger calls to %-style, add exc_info=True and file path to save_configuration error, add exception chaining (from e) throughout
• Ignore regular and inline comments in configfile
• Add 80 unit tests covering all of the above plus thread safety, view sharing, and factory behaviour

Motivation

The configfile module had several subtle parsing bugs and inconsistent behaviors that could corrupt configuration values (e.g., URLs, tokens, or section names) and return incorrect results in some edge cases.

This PR stabilizes the module by fixing multiple correctness issues, tightening error handling, and improving logging. It also refactors parts of the parser to simplify internal tracking and avoid repeated regex compilation.

To prevent regressions and make future changes safer, a comprehensive unit test suite (80 tests) was added, covering parsing behavior, configuration access methods, lifecycle operations, and concurrency aspects.

Tests

tests/util/test_configfile_unit.py: 80 unit tests. Covers parsing, comment handling, deduplication, all read methods, get_section view sharing, add/update/ save lifecycle, get_configparser factory, RLock reentrancy, thread safety, and stale-view-after-reload.