occ_command: switch to std::formatter for enums

Commit 48002498740996ce57bce399960b0f6f2ff6d1df switched to std::format
but missed changing the custom formatter from fmt to std::format.  Add
std::formatter overrides for the enums.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I59e727c42cf8d91d1841daee64bd4d9e066e5151
1 file changed