keep code tree folding state set by hand

[main Alexey]

here is beta:
https://github.com/Alexey-T/CudaText/discussions/5633
it has changes in api:

1.0.460 (app 1.215.6)
* add: on_state new Id APPSTATE_CODETREE_BEFORE_CLEAR
* add: on_state new Id APPSTATE_CODETREE_FOLDED_UNFOLDED
* add: app_proc: PROC_GET_CODETREE_CURRENT_NODE