This changes the start-ostree command to:
compose start-ostree [--size XXXX] [--parent PARENT] [--ref REF] <BLUEPRINT> <TYPE> [<IMAGE-NAME> <PROFILE.TOML>]
Both of them are optional, and if missing a "" is passed to
osbuild-composer. Also adds more tests for all the various possible
options and removes the provider and profile arguments.
(cherry picked from commit 5b0487f47c)
Resolves: rhbz#1859680
This is in preperation for adding more optional arguments. Adds a
generic get_arg function, tests for it, and converts get_size to use it.
(cherry picked from commit 4a4128af23)
Related: rhbz#1859680
