CLI: Add an -auth option to specify authentication profile to use

[fredrikhr]

My proposal is similar to the -env option:
Introduce the -auth or --auth-profile command line option, allowing a user to override the currently in use authentication profile with the authentication profile specified by command line.

Oftentimes I find myself needing to switch between authentication profiles to perform deployment actions across multiple environments and having to remember to first run the pac auth select command introduces a source of possible failure when the wrong authentication profile might have been chosen for the command. This is also common when having to switch between working on two entirely unrelated applications as the selected auth profile is user-global not specific to a workspace.

When thinking about this problem I have realised that this problem has already appeared before and been solved: Originally pac commands would only work against the currently selected environment, and one had to run the pac env select command prior to any operation sequence. However, nowadays all environment-specific pac commands have the -env option to override the currently selected environment with the environment specified by command line instead. This lead me to proposing the exact same strategy for the authentication profile.

Of course, I am not suggesting to change any existing workflows or existing behaviour, I only suggest to add an additional option. User not using the new proposed option would not oberserve any difference in behaviour. Likewise, specifying the authentication profile by command-line should change the selected authentication profile for command that don't specify the argument, similar to the -env option not modifying persistent state either.