[a11y] Deprecate GetIntListAttribute(attribute, value)

This method is being deprecated in place of calling Has...Attribute
followed by Get...Attribute.  The 2 argument version of Get forces
a copy of the int list, where the single argument version returns a
const reference and is thus more efficient.  Though the 2 argument
version is convenient for testing, it was also being used in
production code where efficiency matters.

Bug: 365536926
Change-Id: I91117ffc5fa02e48165ed8b8df413ef49540f9d6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5866855
Reviewed-by: David Tseng <dtseng@chromium.org>
Commit-Queue: Kevin Ellis <kevers@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1357552}