Improve checkbox layout

[donv]

• Indent checkbox into second column for horizontal layout
• Allow overriding the label class, not just add more classes.
• Align label with the top of the first check box in a collection in horizontal layout
• Vertically align check boxes and labels in inline layout.

Since there are breaking changes, overriding the label class and indenting the check box into the second column for horizontal layout, I would like to bump the version number to 5.3 also to indicate that we now support Bootstrap 5.3.

[lcreid]

I share your concern about these being breaking changes, but since we're really fixing stuff that was broken before (mis-aligned fields and labels, for example), I think making the change is reasonable.

I'd like to see what you think about my comments and questions before I approve, but overall I really like what I'm seeing.

[lcreid]

The edge test failures are #691

[donv]

@lcreid Good to merge?

[donv]

I'll go ahead and merge this, then.

[Laykou]

I've noticed this makes it difficult to add help

Previously I could do:

= f.form_group :is_requestable do
    = f.check_box :is_requestable
    .form-text
      = t('activerecord.attributes.group.is_requestable_help') 

Now I need to remove all f.form_group since the offcet is now done twice - wrapped also as part of f.check_box

This now changed and form_group is removed (however it is still mentioned in the readme here: https://github.com/bootstrap-ruby/bootstrap_form/tree/main?tab=readme-ov-file#checkboxes-and-radios

Now it's enough to set just:

= f.check_box :is_requestable

However there is no way how to add additional text like

= f.check_box :is_requestable, help: 'Some explanatino'