Files + text in a separate preview layout.

Expand the image+text flow to allow arbitrary files+text, but only keep
preview code for the single-image use case.

Remove some of the relevant logic from UnifiedContentPreview.

Update headlines to give more clarity in the files+text cases.

Bug: 277958508
Test: Manual testing with ShareTest.
Test: atest IntentResolverUnitTests

Change-Id: Ibdc0688acf43c228ed5cbc0bfd73026bcfada1f2
10 files changed