androiddeployqt: Speed up debug deployment

Debug deployment had a major flaw which made it slower than
just bundling the libraries. For every deployment it would
recursively extract the timestamp of all files from the
remote tmp/ directory. This took about 20 seconds.

I've made some improvements:
1. Just use a single modification.txt file which is updated for every
deployment and only update Qt files that have changed since the last
deployment.

2. Deploy all Qt files in debug deployment instead of just the
dependencies of the app, to make it possible to add dependencies to
the app at a later time without clearing the remote cache.

3. Instead of doing an adb push call for each file, we now just do one
big push after building the local temporary directory.

4. I added a timing mechanism to make it simpler to debug problems
related to this.

Task-number: QTBUG-35401
[ChangeLog][androiddeployqt][QTBUG-35401] Speed up debug deployment.

Change-Id: Ida94c73fc48a0a627203398a86732a94baff1451
Reviewed-by: Daniel Teske <daniel.teske@digia.com>
Reviewed-by: BogDan Vatra <bogdan@kde.org>