style(grid): use native input class insead of tag as selector (#16774)

Author: didimmova

projects/igniteui-angular/core/src/core/styles/components/grid/_grid-theme.scss

@@ -185,12 +185,12 @@
         igx-input-group {
             background: var-get($theme, 'cell-editing-background');
 
-            input {
+            .igx-input-group__input {
                 height: 100%;
                 color: var-get($theme, 'cell-editing-foreground');
             }
 
-            input:focus {
+            .igx-input-group__input:focus {
                 color: var-get($theme, 'cell-editing-focus-foreground');
             }
         }
@@ -270,6 +270,8 @@
 
         .igx-input-group__input {
             padding-inline: sizable(rem(4px), rem(6px), rem(8px)) !important;
+            margin: 0 auto;
+            max-width: 100%;
         }
 
         igx-date-range-picker {
@@ -280,11 +282,6 @@
             display: none;
         }
 
-        input {
-            margin: 0 auto;
-            max-width: 100%;
-        }
-
         %form-group-input {
             // ignore global typography
             font-size: $grid-cell-fs !important;