Add z-index to x-form-item class (#16712)

### What does it do?
Primary goal is to add z-index to x-form-item class. During setup of my
test environment I noticed some critical vulnerabilities were
unaddressed in the package generation files, so I corrected those as
well.

### Why is it needed?
Fixes an issue where the form items can overlap the menu bar, making the
menu unclickable.

### How to test
Open a file to edit in the manager. Scroll down until "Content" ->
"Clear Cache" -> "Refresh URIs" opens over one of the field labels.
Without the fix the text will appear over "Refresh URIs" making it hard
to click. The same happens if you do this for checkboxes and certain
other field elements.

### Related issue(s)/PR(s)
#16711

---------

Co-authored-by: Jason Coward <[email protected]>

Author: matdave

_build/templates/default/sass/_forms.scss

@@ -114,6 +114,7 @@ input::-moz-focus-inner {
   margin: 0;
   outline: 0 none; /* prevent firefox from creating ugly dotted outlines */
   position: relative; /* boundary for absolutely positioned elements */
+  z-index: 1;
 
   /* general styles for form labels, paddings for various form layouts are handled below */
   label.x-form-item-label {

_build/templates/default/sass/_tabs.scss

@@ -85,7 +85,7 @@ ul.x-tab-strip li {
   margin-left: 0;
   padding: 0 12px;
   position: relative;
-  z-index: 5;
+  z-index: 1;
 
   html[dir="rtl"] & {
     float: right;

manager/templates/default/css/index-min.css

@@ -20838,6 +20838,7 @@ input::-moz-focus-inner {
     /* prevent firefox from creating ugly dotted outlines */
     position: relative;
     /* boundary for absolutely positioned elements */
+    z-index: 1;
     /* general styles for form labels, paddings for various form layouts are handled below */
     /* label.x-form-item-label */
     /* is outside of the label */
@@ -22938,7 +22939,7 @@ ul.x-tab-strip li {
     margin-left: 0;
     padding: 0 12px;
     position: relative;
-    z-index: 5;
+    z-index: 1;
 }
 html[dir=rtl] ul.x-tab-strip li {
     float: right;