[wip] PyREPL: Add ctrl+up/down for multiline history

[edvilme]

Currently, the up/down keys move the cursor in that direction inside the current code block until it reaches the beginning/end, then it goes to the previous/next. However, when traversing history with lots of multiline blocks, this can be a cumbersome process.

This PR introduces the ability to traverse history one block at a time using the CTRL+Up or CTRL+Down keys.

Originated from https://discuss.python.org/t/pyrepl-add-ctrl-up-down-for-multiline-history-retrieving/107779

[hugovk]

Good news, this is already implemented as Ctrl+P and Ctrl+N!

cpython/Lib/_pyrepl/historical_reader.py

Lines 56 to 71 in a064b32

	class next_history(commands.Command):
	def do(self) -> None:
	r = self.reader
	if r.historyi == len(r.history):
	r.error("end of history list")
	return
	r.select_item(r.historyi + 1)
	class previous_history(commands.Command):
	def do(self) -> None:
	r = self.reader
	if r.historyi == 0:
	r.error("start of history list")
	return
	r.select_item(r.historyi - 1)

cpython/Lib/_pyrepl/historical_reader.py

Lines 261 to 262 in a064b32

	(r"\C-n", "next-history"),
	(r"\C-p", "previous-history"),

See https://discuss.python.org/t/pyrepl-add-ctrl-up-down-for-multiline-history-retrieving/107779/4 for more.