[BUGFIX] Fix margins of form labels

Labels within FormEngine are bold, but due to Boostrap 5
all labels in all places were bold and created margin, making
the rendering of the rest of the TYPO3 Backend hard-to-grasp,
as well as FormEngine not allowing to have a different view
for labels of fields, and labels of actual form elements.

This change adapts the margin and font-weight accordingly.

Resolves: #93519
Releases: master
Change-Id: I3bf0fda432cf43309fe3909a22784609ddeaa904
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/67952
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Richard Haeser <richard@richardhaeser.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Richard Haeser <richard@richardhaeser.com>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Benni Mack <benni@typo3.org>

Build/Sources/Sass/typo3/_main_form.scss

@@ -87,7 +87,7 @@ label {
 }
 
 .form-control-wrap {
-    margin: 9px 0;
+    margin: 0 0 0.5rem;
 }
 
 .form-control-holder {
@@ -112,6 +112,12 @@ label {
             top: 100%;
         }
     }
+
+    > label,
+    > .form-label {
+        font-weight: 600;
+        margin: 0.25rem 0 0.5rem;
+    }
 }
 
 .form-control[disabled],

Build/Sources/Sass/variables/_main.scss

@@ -146,7 +146,8 @@ $input-color-placeholder: $gray-300;
 $input-color-disabled: $gray-600;
 $input-height-large: (ceil($font-size-large * $line-height-large) + ($padding-large-vertical * 1.6) + 2);
 $input-border-color: $gray-500;
-$form-label-font-weight: 700;
+$form-label-font-weight: 400;
+$form-label-margin-bottom: 0.25rem;
 $form-switch-width: 2.5em;
 
 // Navbar