With this CL, ASH now relies on the host package name passed by identity
sharing API only, not by service connection or startActivityForResult.
Also:

- records a boolean histogram indicating whether CustomTabs/Browser
  are launched with shared identity by hosts.
- simplifies Activity.getCallingActivity -> Activity.getPackageName
  with a single call Activity.getCallingPackage. This becomes
  possible as the latter works in reliable fashion on N+.

(cherry picked from commit 41495d05b108fa7bda85d1b915ecb38afeb8e952)

Bug: 330118241
Change-Id: I95f37d063ed35334070f435fcb8c61e8ec20fbb4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5374029
Reviewed-by: Kevin Grosu <kgrosu@google.com>
Commit-Queue: Jinsuk Kim <jinsukkim@chromium.org>
Cr-Original-Commit-Position: refs/heads/main@{#1276919}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5397796
Reviewed-by: Michael Thiessen <mthiesse@chromium.org>
Reviewed-by: Sinan Sahin <sinansahin@google.com>
Cr-Commit-Position: refs/branch-heads/6367@{#276}
Cr-Branched-From: d158c6dc6e3604e6f899041972edf26087a49740-refs/heads/main@{#1274542}