Adds accuracy to the frame rate measurements used to configure RC smoothing. Prevents looptime delays and jitter from affecting the calculations. Significantly improves the accuracy of the measurement in cases where CPU load is high.
Implemented so that each protocol can individually provide the functionality if appropriate. If a protocol doesn't support the more granular measurement then the system will fallback to the original measurement calculated in the RX task.
Remove the giant `select` block that contained all the code to generate the elements and transition them to individual functions called only when the element is active. Simplifies the code and results in a performance improvement as it's not necessary to fall through the large `select` statement for every element that will be drawn. The individual functions and the element to function mapping are moved to a new `osd_elements.c` file.
Moved the OSD related code files to a new `osd/` directory.
Also pre-analyze the active elements and only process those that are active. This also saves processing as it's not necessary to loop through all 50 or so elements when only a couple are active.
Various other cleanup and removal of stale or unnecessary code.
In the default configuration the element drawing phase of the OSD task is reduced from ~51us to ~35us - resulting in about a 30% decrease in processing time.
