test: convert more test skips to known failures

[reubeno]

Some of the tests previously being skipped could be run under cargo nextest in our compat test harness's "pty mode" instead. Some still fail, but at least they can be run and show up as known failures.

[github-actions]

Test Results

  2 files    8 suites   53s ⏱️
423 tests 423 ✅ 0 💤 0 ❌
846 runs  846 ✅ 0 💤 0 ❌

Results for commit e6a7b11.

[github-actions]

Performance Benchmark Report

Benchmark name	Baseline (μs)	Test/PR (μs)	Delta (μs)	Delta %
expand_one_string	3.36 μs	3.36 μs	0.00 μs	⚪ Unchanged
instantiate_shell	59.23 μs	59.40 μs	0.16 μs	⚪ Unchanged
instantiate_shell_with_init_scripts	24958.27 μs	24998.94 μs	40.67 μs	⚪ Unchanged
parse_bash_completion	5694.14 μs	5706.17 μs	12.04 μs	⚪ Unchanged
parse_sample_script	9.04 μs	8.98 μs	-0.06 μs	⚪ Unchanged
run_echo_builtin_command	92.06 μs	91.99 μs	-0.07 μs	⚪ Unchanged
run_one_builtin_command	111.10 μs	114.18 μs	3.08 μs	🟠 +2.77%
run_one_external_command	1863.63 μs	1951.72 μs	88.09 μs	🟠 +4.73%
run_one_external_command_directly	949.59 μs	952.06 μs	2.46 μs	⚪ Unchanged

Code Coverage Report: Only Changed Files listed

Package	Base Coverage	New Coverage	Difference
brush-core/src/shell.rs	🟢 77.22%	🟢 77.83%	🟢 0.61%
brush-core/src/sys/unix/signal.rs	🟠 67.65%	🟠 64.71%	🔴 -2.94%
brush-shell/src/args.rs	🟠 64.29%	🟠 66.67%	🟢 2.38%
brush-shell/src/main.rs	🟢 91.43%	🟢 92.86%	🟢 1.43%
Overall Coverage	🟢 76.09%	🟢 76.13%	🟢 0.04%

Minimum allowed coverage is 70%, this run produced 76.13%