fest(flysky): Flysky Gimbal 2.0 Sync Sampling Support

[richardclli]

Flysky works out a new version of firmware that can support sync sampling:

1. Upon init the gimbal will operate in backward compatible mode (i.e. old EdgeTX will works after the gimbal firmware is upgraded)
2. New firmware will check the version of the firmware to see if sync mode is supported
3. New driver will send command to the gimbal for sync sampling

The gimbal driver changes:

1. It will automatic obtain the version of the gimbal to check if sync sampling is available
2. The default operation mode is backward compatible mode, will switch to sync modes only when new version of gimbal firmware is detected
3. Based on sampling frequency, the driver will automatically switch to sync sampling mode (<= 400Hz - switching threshold) or sync resampling mode (> 400Hz)

Testing:

1. Not breaking the operation of existing old gimbals including the gimbal of GX12
2. Flysky firmware seems to have some problems now, trying to verifying with them.