Add cache to Python block navigation functions

Add cache to Python block navigation functions

* lisp/progmodes/python.el (python-nav-cache)
(python-nav-cache-tick): New variables.
(python-nav-cache-get, python-nav-cache-set)
(python-nav-with-cache): New functions.
(python-nav-beginning-of-block, python-nav-end-of-block): New
wrapper functions.
(python-nav--beginning-of-block): Renamed from
'python-nav-beginning-of-block'.
(python-nav--end-of-block): Renamed from
'python-nav-end-of-block'.  (Bug#77620)

(cherry picked from commit 9ae82726d8ea4530f26f2baa16b705ba3cd71834)