Fixes #5822

Majorly, the change affects 2 places in the UI. The Clear Browsing
Data… option in the History menu and the Clear Browsing Data Now…
button in the Security tab in Preferences. We store the state of the
toggled options when the user clears anytime, so that the next time
he/she opens this dialog, the options are pre-populated as per the last
selected options

From a technical perspective, we have moved away from saving the
current state of the SwitchControls in the windowState. We only save
the visibility on the windowState. The whole state is managed by the
panel itself and just updates the appState on clicking clear.

Fixes #4082

Making the Clear Browsing Data panel stateful

restyle preferences payments

Add focus ring to about page form elements

Add Paste Without Formatting to context menu

Closes #5972

- Set -webkit-appearance:none
- Set the caret down SVG file (created by @bradleyrichter) as the background-image
- Set the outline inside the input element
- Set height:2rem to make the height consistent
- Moved properties in .form-control to the input and select element
- Removed box-shadow properties from the input and select element under .bookmarkForm
- Set specific properties to input in #navigator

The caret down SVG file will be replaced with the sprite PNG later (See #5891)

Auditors:

Test Plan:
1. Open about:preferences
2. Make sure the text entry fields with active edit state have the rectangle inside them
3. Make sure the drop down arrows are styled properly
4. Open another page in a new tab
5. Open the shield from the top right lion icon
6. Make sure the drop down arrows are styled properly
7. Bookmark about:preferences
8. Make sure the input and select elements are styled consistently on the bookmark dialog