[Fuchsia] Fix blink layoyut tests to avoid 'pm install' dependency

Blink layout tests were not running properly after `pm install` command
was removed. Added move package installation logic from run_pacakge.py
to Target class and update layout tests runner to call
target.InstallPackage() instead of running `pm install`.

Also removed invalid Fuchsia-specific test expectations that were
added since the test started failing.

Change-Id: I86ad072d0725042f695b84a48ef132b65d32b963
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1526692
Commit-Queue: Sergey Ulanov <sergeyu@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Reviewed-by: Kevin Marshall <kmarshall@chromium.org>
Auto-Submit: Sergey Ulanov <sergeyu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#642048}
16 files changed