v5: Floating labels (#30449)

* v5: Promote floating labels example to component

- Adds new .form-floating
- Stubs out basics of a docs page
- Removes existing Example

* Update floating labels to support .form-select, make inputs and selects more consistent

- To do this, I made the .form-control and .form-select consistent in min-height vs height
- Removed some unused variables now
- Updated -color to be the -color because I don't know why this was any different before
- Update page to include some examples for layout, validation, and value
- Rewrite styles to not modify padding, but instead transform and opacity

* Streamline and bulletproof some things

- Apply some optimizations from code review
- Removed unecessary properties from the label
- Add some comments for what properties are required
- Move from fixed height for labels to height 100% so we can support textareas
- Improve docs a little bit, add ToC

* Move some values to variables, switch from scaling font-size to scale, update transforms

* Bring over changes from #30966 and add to them to tighten things up

* Delete the now unused example images

* Fix typo

* Allowlist the calc function

* Add transform-origin, update transform values

* Test out autofill fix

* Fix linter issue

* Mention it in the migration guide

* Bump bundlesize

* Add one more variable per review

* Shave .25rem off the height

Co-authored-by: XhmikosR <xhmikosr@gmail.com>

scss/_variables.scss

@@ -648,7 +648,7 @@ $input-bg:                              $white !default;
 $input-disabled-bg:                     $gray-200 !default;
 $input-disabled-border-color:           null !default;
 
-$input-color:                           $gray-700 !default;
+$input-color:                           $body-color !default;
 $input-border-color:                    $gray-400 !default;
 $input-border-width:                    $input-btn-border-width !default;
 $input-box-shadow:                      $box-shadow-inset !default;
@@ -733,7 +733,6 @@ $input-group-addon-color:               $input-color !default;
 $input-group-addon-bg:                  $gray-200 !default;
 $input-group-addon-border-color:        $input-border-color !default;
 
-
 $form-select-padding-y:             $input-padding-y !default;
 $form-select-padding-x:             $input-padding-x !default;
 $form-select-font-family:           $input-font-family !default;
@@ -824,6 +823,14 @@ $form-file-padding-x-lg:          $input-padding-x-lg !default;
 $form-file-font-size-lg:          $input-font-size-lg !default;
 $form-file-height-lg:             $input-height-lg !default;
 
+$form-floating-height:            add(3.5rem, $input-height-border) !default;
+$form-floating-padding-x:         $input-padding-x !default;
+$form-floating-padding-y:         1rem !default;
+$form-floating-input-padding-t:   1.625rem !default;
+$form-floating-input-padding-b:   .625rem !default;
+$form-floating-label-opacity:     .65 !default;
+$form-floating-label-transform:   scale(.85) translateY(-.5rem) translateX(.15rem) !default;
+$form-floating-transition:        opacity .1s ease-in-out, transform .1s ease-in-out !default;
 
 // Form validation