feat(arithmetic): support explicit base#literal in arithmetic

[reubeno]

Implements support for arithmetic literals like 2#1010 and 16#32f.

The native Rust facility to parsing integers with an explicit radix only supports base 2-36. That's pretty reasonable, but bash technically supports up through base 64. For now, we do our best with the native facilities.

[github-actions]

Test Results

    2 files      9 suites   1m 38s ⏱️
  689 tests   689 ✅ 0 💤 0 ❌
1 364 runs  1 364 ✅ 0 💤 0 ❌

Results for commit 8b4f552.

[github-actions]

Performance Benchmark Report

Benchmark name	Baseline (μs)	Test/PR (μs)	Delta (μs)	Delta %
clone_shell_object	18.21 μs	18.03 μs	-0.18 μs	⚪ Unchanged
eval_arithmetic	0.17 μs	0.17 μs	0.00 μs	⚪ Unchanged
expand_one_string	1.84 μs	1.79 μs	-0.04 μs	⚪ Unchanged
for_loop	22.10 μs	22.02 μs	-0.09 μs	⚪ Unchanged
function_call	2.29 μs	2.30 μs	0.00 μs	⚪ Unchanged
instantiate_shell	57.21 μs	56.42 μs	-0.79 μs	🟢 -1.38%
instantiate_shell_with_init_scripts	21162.00 μs	21230.09 μs	68.09 μs	⚪ Unchanged
parse_bash_completion	1682.13 μs	1692.29 μs	10.16 μs	⚪ Unchanged
parse_sample_script	1.76 μs	1.79 μs	0.03 μs	🟠 +1.70%
run_echo_builtin_command	15.09 μs	15.36 μs	0.27 μs	⚪ Unchanged
run_one_external_command	2371.51 μs	2192.19 μs	-179.32 μs	🟢 -7.56%
tokenize_sample_script	2.93 μs	2.91 μs	-0.02 μs	⚪ Unchanged

Code Coverage Report: Only Changed Files listed

Package	Base Coverage	New Coverage	Difference
brush-core/src/options.rs	🟢 92.39%	🟢 93.48%	🟢 1.09%
Overall Coverage	🟢 78.24%	🟢 78.27%	🟢 0.03%

Minimum allowed coverage is 70%, this run produced 78.27%

Test Summary: bash-completion test suite

Outcome	Count	Percentage
✅ Pass	1331	63.38
❗️ Error	227	10.81
❌ Fail	157	7.48
⏩ Skip	370	17.62
❎ Expected Fail	14	0.67
✔️ Unexpected Pass	1	0.05
📊 Total	2100	100.00