docs: Update Imageview JavaDoc comments

- fix typographic errors (misspellings)
- Simplified the overview to essential info
- included a code example for common TextView usecase
- adds missing javadoc description and param for setScroller method
- standardize “text view” as TextView to promote consistency

Change-Id: I7d614430599537c3ff5999f9c139cc896f142cde
From: BNR vendor, Project 01, android-developer-documentation/pull/1

Test: docs-only change. Tested with a check build