Pull Request Diff tab : Form field causes unexpected change

Issue Summary

A change of context occurs without warning when the user changes the setting of a user interface control.
Element description: Filter file tree" and "Search code" search options.

Steps to Reproduce

1. Open the Pull Request.
2. In the Pull request, navigate to the Diff tab and activate it.
3. Select the Search code button
4. In the available input field, try searching for some code part and observe the results available.

Actual Results

In the Diff section, for the Search code input field, when the user tries to search for some code in the search input field, results are available automatically on user input. These available results are not conveyed to the screen reader user. The dynamic appearances are not indicated to the user and hence the user would not be able to identify the results and the results are available without any submit button. 

Expected Results

The results should be only available when the user submits the form or on "Enter" keystroke submit event. 
Provide an aria-live="polite" to the availble results <div> element.

Ensure the results are announced to the screen reader user.

Refer to the following links for an accessible implementation:
https://www.w3.org/WAI/WCAG21/Understanding/on-input 
https://developer.mozilla.org/en-US/docs/Web/Accessibility/ARIA/ARIA_Live_Regions 

Screenshot

Screen Recording

Screen Recording 2022-09-07 at 8.53.56 AM.mov

Workaround

Currently, there is no known workaround for this behavior. A workaround will be added here when available.

Bug Ref: 737330