Fix Media Notification click in TWA

WebappLocator is the responsible for locating the running WebappActivity upon receiving new notification it order to route it correctly, TWA passes through this flow but it doesn't match the if condition so it doesn't work.

Since this WebappLocator returns BaseCustomTabActivity and all the variable names matches this too then it makes sense to rename it to CustomTabLocator to make the name more meaningful and the class will be helpful for solving other cases too instead of duplicating the logic or over-engineering the design by creating BaseLocator.

Bug: 1358863
Change-Id: Ic8d6030a358cbe0e122e4ca807447cc8f4ba3bf0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4335548
Reviewed-by: Peter Conn <peconn@chromium.org>
Commit-Queue: Sayed Elabady <elabadysayed@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1122310}