Drop Regex

[LinuxBoy-96]

I’ve decided that we can drop Regex as a dependency.
In fact, we need very little functionality from it.

This PR introduces regex.rs, a custom implementation to replace the crate, as I believe the risk is negligible.

With this change, the compiled release binary size goes from 3976 KB down to 2440 KB —
a reduction of 1536 KB, or 38.6%.

From my testing, it works flawlessly.

You are very welcome 😎

[ryuichiueda]

I have also wanted to remove it. I will test your implementation. Thank you!

[ryuichiueda]

Oops I found the following difference. (test_compound.bash in https://github.com/shellgei/rusty_bash_test )

bash-5.2$ A=a ; [[ $A =~ a ]] ; echo $?
0
alpha-tmp🌵~/GIT/rusty_bash(debug)🍣 A=abc ; [[ $A =~ a ]] ; echo $?
1

In the test script, errors found in LINE 806, 809, 812, ...

Could you fix them?

Tnank you