Benchexec

- `table-generator` computes scores according to SV-COMP'24 scoring scheme.
This changes only the scoring for witness-validation results.
- Support for property files at HTTP(S) URLs in `table-generator`.
Tables can already be produced not only from local result files, but also from files that are downloaded on the fly.
Now this also works for results with property files.
- Fix for tool-info module `witnesslint`.

- Two tool-info modules improved.

- Tool-info modules can now provide URLs that will be used for links in HTML tables.
There are two new methods, `project_url()` and `url_for_version()` that can be implemented, and `table-generator` will put links to these URLs in the summary table of the HTML tables (for the tool name and the version). Most existing tool-info modules were extended with `project_url()`.
- Many new and improved tool-info modules.

The big change in this release is the long-awaited support for cgroups v2!
Please refer to the [installation instructions](https://github.com/sosy-lab/benchexec/blob/master/doc/INSTALL.md) for how to use it (on Ubuntu/Debian, installing our package is enough). Note that this of course has not been tested yet on as many different systems as our support for cgroups v1, so there might still be some rough edges. Please provide [feedback](https://github.com/sosy-lab/benchexec/issues/new) if you encounter any problems or have questions. On systems with cgroups v1, everything should work the same way as before.
Thanks a lot to globin for providing the implementation of this!

There are also some other minor improvements:

- If the system administrator has configured a lower frequency limit than what the CPU supports, BenchExec now reports this limit as the CPU speed.
- Fixes in `table-generator` for result files that conform to the specification but were not produced by `benchexec`.
- A few minor improvements for better integration with Podman containers.

- Even more robust handling of child cgroups created within a run
Despite the improvements from BenchExec 3.13 there could be crashes because sometimes cgroups vanish while we iterate over them. Avoiding this did not fully work, maybe due to some delays in the kernel, so now we handle this.
- Actually fix handling of non-printable characters in environment variables.
The fix that was part of BenchExec 3.12 only worked if a non-printable character was the first character of the value of the environment variable.

This release works only on Python 3.7 and newer!

- Improve performance of the "Merging results" step of `table-generator`.
In the common case of all run sets having the same set of tasks, this step is now much faster.
- Avoid deadlock in `table-generator` for cases with many child processes and heavy system load.
- On systems with many cores and if there are many input files or columns, `table-generator` will now use more than 32 child processes.
- Support the scoring schema used in SV-COMP'23 for witness validators, and show the witness category as part of the task identifier in tables.
Note that just like for the category `correct-unconfirmed` external postprocessing of the results is necessary for this.
- If the pattern inside a `<propertyfile>` tag in the benchmark definition does not match a file, BenchExec now terminates with an error instead of just logging a warning.
- Improved logging in `table-generator`.
The log messages about missing run results and missing properties, which could occur many times in certain use cases, are now omitted. Instead, some numbers about the size of the resulting tables and the number of missing results will be logged.