Separate dirty part of file-name status line element into its own file-dirty element

[cbclemmer]

attempts to close #4686

Adds a new "file-dirty" status line element that can replace the [+] symbol that appears after the file name. This allows the element to be added before the "file-name" element so the dirty symbol will be visible for long file/directory names. Adds logic to keep the dirty element after the "file-name" element if it is not in the list. This keeps current config files and the default configuration working as they were before while allowing the dirty element to be placed wherever the config file specifies.

[the-mikedavis]

Let's call this "FileModificationIndicator"

[cbclemmer]

@the-mikedavis Ok, I found a reference to dirty somewhere so that's why I called it that.

[cbclemmer]

@the-mikedavis I changed it along with the other related variables.

[cbclemmer]

@kirawi Is there anything you are waiting for me on this PR?

[kirawi]

@the-mikedavis I feel like this is a fairly uncontroversial change.

[cbclemmer]

@kirawi @the-mikedavis The tests are passing now. I didn't see that before.

[theteachr]

We could make the element customizable.

[theteachr]

I believe this one needs an update in the configuration docs.

[the-mikedavis]

Ah good catch, a new line for this should be added in this table https://github.com/helix-editor/helix/blob/0a7c697dd785111626c8f47a36e07381f55c2e83/book/src/configuration.md#L93

[theteachr]

Created https://github.com/helix-editor/helix/pull/6036 to update the docs.