Introduce FontsContract.requestFont and deprecate Typeface.create

Since background fetch should be synchronized with life cycle of
Activities, so should not create new background thread inside this
method. Not to break existing apps, mark as deprecated and will be
removed from public API untile next release.

New API accepts Handler so that the developer can pass their own thread
.

Test: TBD
Bug: 37253785
Change-Id: I87fdc6a354a829db679253824f42489f25698fa0