deps: Remove the use of the `regex` crate

[bryantbiggs]

• Instead of using the regex crate to ensure the path ends at the correct / which is a bit heavy handed for this use case, it has been replaced with an iterator based implementation
• Simplify longest common prefix logic - this was pinched from here, the original logic seemed a bit verbose

[mxpv]

I wonder if we need regex dependency at all. we only use it in trim_flawed_dir.

Given these test cases:

tcases.push(("/.foo-_bar/foo", "/.foo-_bar/".to_string()));
tcases.push(("/.foo-_bar/foo/", "/.foo-_bar/foo/".to_string()));
tcases.push(("/.foo-_bar/foo/bar", "/.foo-_bar/foo/".to_string()));
tcases.push(("/.foo-_bar/foo/bar/", "/.foo-_bar/foo/bar/".to_string()));

I feel like it should be relatively straightforward to rewrite it without regular expressions.

WDYT?

[bryantbiggs]

I wonder if we need regex dependency at all. we only use it in trim_flawed_dir.

Given these test cases:

tcases.push(("/.foo-_bar/foo", "/.foo-_bar/".to_string()));
tcases.push(("/.foo-_bar/foo/", "/.foo-_bar/foo/".to_string()));
tcases.push(("/.foo-_bar/foo/bar", "/.foo-_bar/foo/".to_string()));
tcases.push(("/.foo-_bar/foo/bar/", "/.foo-_bar/foo/bar/".to_string()));

I feel like it should be relatively straightforward to rewrite it without regular expressions.

WDYT?

Great point! Let me know what you think of the implementation