[3.14] gh-144415: Android testbed fixes (GH-142912) (#144416)

Modifies handling of `.gz` files in Android app payloads, and ensures that
when the Android testbed streams logs, stream flushes aren't treated as
newlines. This improves the output of test suites that use "one dot per test"
progress indicators.
(cherry picked from commit cb1dc91dcb1eb6637d1c79b34a0bab728939f717)

Co-authored-by: Malcolm Smith <smith@chaquo.com>