fix(completion): fix -- handling in getopts

[reubeno]

• Apply the same workaround to getopts that was added for echo in #147.
• Add a test case to cover -- being passed as the first arg to getopts after the variable name.

[github-actions[bot]]

Test Results

  2 files    9 suites   1m 7s ⏱️ 497 tests 497 ✅ 0 💤 0 ❌ 983 runs  983 ✅ 0 💤 0 ❌

Results for commit 610f5cfb.

[github-actions[bot]]

Performance Benchmark Report

Benchmark name	Baseline (μs)	Test/PR (μs)	Delta (μs)	Delta %
expand_one_string	3.42 μs	3.42 μs	-0.00 μs	⚪ Unchanged
instantiate_shell	60.26 μs	60.34 μs	0.08 μs	⚪ Unchanged
instantiate_shell_with_init_scripts	30563.22 μs	30320.03 μs	-243.20 μs	⚪ Unchanged
parse_bash_completion	2727.85 μs	2723.81 μs	-4.04 μs	⚪ Unchanged
parse_sample_script	4.13 μs	4.22 μs	0.09 μs	🟠 +2.30%
run_echo_builtin_command	90.76 μs	90.74 μs	-0.02 μs	⚪ Unchanged
run_one_builtin_command	110.05 μs	109.55 μs	-0.50 μs	⚪ Unchanged
run_one_external_command	1966.71 μs	1938.36 μs	-28.35 μs	🟢 -1.44%
run_one_external_command_directly	1002.31 μs	1004.64 μs	2.33 μs	⚪ Unchanged

Code Coverage Report: Only Changed Files listed

Package	Base Coverage	New Coverage	Difference
brush-core/src/builtins/getopts.rs	🟢 94.81%	🟢 95.12%	🟢 0.31%
brush-core/src/jobs.rs	🔴 42.42%	🔴 37.23%	🔴 -5.19%
brush-core/src/shell.rs	🟢 78.66%	🟢 78.09%	🔴 -0.57%
brush-shell/src/main.rs	🟢 90.85%	🟢 90.2%	🔴 -0.65%
Overall Coverage	🟢 73.54%	🟢 73.44%	🔴 -0.1%

Minimum allowed coverage is 70%, this run produced 73.44%