Add lua-send-string-max-size and lua-send-region-chunked

[immerrr]

This PR adds lua-send-string-max-size variable that limits the size of the data that's sent to subprocess in one go. It also introduces lua-send-region-chunked function that sends the code in chunks that don't exceed given size to sidestep the size limitation.

[astoff]

FWIW, the variable comint-max-line-length, new in Emacs 28, seems related to this.