[EuiDataGrid] Fix inconsistent focus halo (#5522)

* Modifies Sass to keep consistency in focus halo

The outline property for the control columns of the EuiDataGrid element is modified in order to keep color theme consistent along the grid.

* Change ButtonIcon focus properties

The outline of euiButtonIcons is moved to the _data_grid_data_row in order to not modify outlines in buttons outside of euiDataGrids

* Update CHANGELOG.md

Added a more complete description of the changes made.

* Review changes

The following changes are made:
* CHANGELOG.md: Title is changed to enhancements and description is updated.
* _form.scss: File is restored to its original state, as it was modyfing a whole mixin.
* _dara_grid_data/header_row.scss: The property from the mixin is moved to each of these files to overwrite the checkbox modifiers.

* Updated the outline color in `euiCustomControlFocused` mixin to use
`$euiFocusRingColor`

Co-authored-by: Elizabet Oliveira <elizabet.oliveira@gmail.com>
Co-authored-by: Elizabet Oliveira <elizabet.oliveira@elastic.co>

CHANGELOG.md

@@ -1,6 +1,7 @@
 ## [`main`](https://github.com/elastic/eui/tree/main)
 
-No public interface changes since `45.0.0`.
+- Updated the outline color in `euiCustomControlFocused` mixin to use 
+`$euiFocusRingColor` instead of `currentColor` ([#5479](https://github.com/elastic/eui/pull/5479))
 
 ## [`45.0.0`](https://github.com/elastic/eui/tree/v45.0.0)
 

src/global_styling/mixins/_form.scss

@@ -344,13 +344,14 @@
   // Requires a selector to work with the Amsterdam outline styles
   @if ($amsterdamSelector) {
     + #{$amsterdamSelector} {
-      outline: $euiFocusRingSize solid currentColor;
+      outline: $euiFocusRingSize solid $euiFocusRingColor;
+      outline-offset: 2px;
     }
 
     // Chrome
     &:focus-visible + #{$amsterdamSelector} {
-      outline-style: auto;
-      outline-offset: 3px;
+      outline: $euiFocusRingSize solid $euiFocusRingColor;
+      outline-offset: 2px;
     }
 
     &:not(:focus-visible) + #{$amsterdamSelector} {