python-common/cryptotools: unify and organize all endpoint functions

python-common/cryptotools: unify and organize all endpoint functions

Lightly reorganize and make the "endpoint" functions in cryptotools.py more
consistent and uniform. Use small functions for input and output
handling so that the handling is done the same way throughout. Pass a
pre-constructed crypto caller via the args to then endpoint functions.
Make generating the private key it's own named function rather than
one single (and only) function with overloaded behavior controlled by
a cli switch.

Signed-off-by: John Mulligan <jmulligan@redhat.com>
(cherry picked from commit 552d7b4373afa1a93fe47ce234560b9c8485321d)

Resolves: rhbz#2401206