v2.1.1: Start Development of NNStreamer 2.1.1 (2.2 RC2)

This is the version marking for 2.1.1 development start.
As 2.1.0 is started on Sep 28 2021, the change is huge.

2.1.0 -> 2.1.1
- Tizen 7.0 M1 RCx preparation and NNStreamer Mini Summit 2022-04 release.

- NNStreamer-Edge refactoring (module for Among-Device AI (a.k.a. Edge-AI))
        - Ongoing effort of nnstreamer-edge separation from nnstreamer.
        - In the future, nnstreamer-edge will provide among-device AI functions and nnstreamer will provide gstreamer plugins for such functions. Non-gstreamer systems may connect to nnstreamer-edge based pipelines without gstreamer as clients.
        - NNStreamer-Edge will be using AITT as its default backend, leaving protocol issues to AITT.
        - In the future, nnstreamer-edge will be compatible with non-Linux ultra-lightweight systems (e.g., Tizen-RT)

- ML-Service API preparation is going on at api.git.

- Major features
        - MQTT timestaamping w/ NTP. (later will be migrated to nnstreamer-edge & aitt)
        - Query (later will be migrated to nnstreamer-edge & aitt): robustness support, mqtt-hybrid protocol, performance fixes for multi-clients.
        - More coverage for SNPE support: quantized model support, SNPE dimension bug workaround, fixes from/for production team.
        - Flexible tensor support w/ decoder, converter, flatbuffer.

- Minor features
        - MQTT unittest basis, generic stream support, android support, timeout handling, ... (and many!)
        - Utility functions exported for plugin writers.
        - Tensorflow-lite delegation refactored for generality: may use XNNPACK more easily.
        - Tensorflow-lite multi-lib support.
        - PyTorch: support complex output tensor formats.
        - NNStreamer multi-lib support.
        - Decoder: boundingbox-yolov5
        - Filter: TRIx-Engine support. (NPUs of Samsung 2022 TV)
        - Docker support refactored and cleaned up.

- Fixes
        - ARMNN build errors.
        - Android errors
        - Build errors with recent compiler updates. (gcc 11)
        - Fixes upstreamed from productions
        - Errors w/ library updates: Lua >= 5.3, GLib >= 2.68
        - Regression fixes: openvino, edgetpu, tensorrt
        - Memory leaks in C++ subplugin infra.

- Known issues: PPA/Launchpad build broken!

Signed-off-by: MyungJoo Ham <[email protected]>