feat: implement alternate arithmetic for syntax

[reubeno]

This is for one of the parts of #743.

It's an (undocumented?) alternate form of arithmetic-for, where you can do something like:

for ((i = 0; i < 10; i++)) {
    echo $i
}

...without the usual ; do and done.

[github-actions]

Test Results

    3 files     23 suites   6m 11s ⏱️
1 111 tests 1 111 ✅ 0 💤 0 ❌
3 313 runs  3 313 ✅ 0 💤 0 ❌

Results for commit 548811b.

[github-actions]

Performance Benchmark Report

Benchmark name	Baseline (μs)	Test/PR (μs)	Delta (μs)	Delta %
clone_shell_object	17.73 μs	17.70 μs	-0.02 μs	⚪ Unchanged
eval_arithmetic	0.14 μs	0.15 μs	0.00 μs	⚪ Unchanged
expand_one_string	1.99 μs	1.99 μs	-0.01 μs	⚪ Unchanged
for_loop	22.41 μs	22.35 μs	-0.07 μs	⚪ Unchanged
function_call	2.73 μs	2.60 μs	-0.13 μs	⚪ Unchanged
instantiate_shell	58.01 μs	58.64 μs	0.63 μs	⚪ Unchanged
instantiate_shell_with_init_scripts	23951.85 μs	24516.61 μs	564.76 μs	🟠 +2.36%
parse_bash_completion	2065.67 μs	2014.04 μs	-51.63 μs	⚪ Unchanged
parse_sample_script	2.04 μs	1.92 μs	-0.11 μs	🟢 -5.50%
run_echo_builtin_command	15.91 μs	15.75 μs	-0.16 μs	⚪ Unchanged
run_one_external_command	2360.15 μs	2388.22 μs	28.07 μs	🟠 +1.19%
tokenize_sample_script	3.51 μs	3.50 μs	-0.01 μs	⚪ Unchanged

Code Coverage Report: Only Changed Files listed

Package	Base Coverage	New Coverage	Difference
brush-parser/src/parser.rs	🟢 95.41%	🟢 95.43%	🟢 0.02%
Overall Coverage	🟢 71.71%	🟢 71.72%	🟢 0.01%

Minimum allowed coverage is 70%, this run produced 71.72%

Test Summary: bash-completion test suite

Outcome	Count	Percentage
✅ Pass	1345	63.77
❗️ Error	216	10.24
❌ Fail	179	8.49
⏩ Skip	354	16.79
❎ Expected Fail	14	0.66
✔️ Unexpected Pass	1	0.05
📊 Total	2109	100.00