Slipcover

This release:
- adds `--version` to the command flags, to display SlipCover's version and exit;
- adds scanning for files never executed in the directories passed with `--source`, so that these, too, are included in the output;
- adds a summary line to the text version of the coverage results;
- fixes bugs computing the destination of certain branches when they occur within a `try` (including `except`, `except*`, `try`-`else` and `finally`). This affects only the branch destination shown, not their existence, counting, or statistics.

This release:

- adds Python 3.12 support, based on the new PEP669 (sys.monitoring) API, rather than bytecode rewriting;
- under Python 3.12, limits support for branch coverage to source files with less than ~32k lines. This is to facilitate adopting PEP669;
- changes the version number to 1.0.1, as this project is now (far) beyond being experimental.

This release fixes a bug which apparently only affects Python 3.10 when using branch coverage.

This release:
- fixes a bug instrumenting for branch coverage. The bug was leading to crashes during de-instrumentation on PyPy;
- continues the work towards making Slipcover more useful for guiding fuzzing;

Many thanks to cfbolz for figuring this bug out, including an [MRE](https://en.wikipedia.org/wiki/Minimal_reproducible_example) for it!

This version makes no visible changes to Slipcover when used as a coverage analyzer.
It starts to improve Slipcover's `import` interface, making it easier to use for coverage-guided fuzzing.

This release:
- adds `--skip-covered` to skip fully (100%) covered files when printing coverage, suggested by LilyFoote;
- adds `--fail-under T` to have Slicover fail with a return code of 2 if the overall coverage is less than `T`, suggested by rec;
- fixes a division by 0 when printing out coverage for empty files on Python 3.11; thank you, diceroll123!