tctl - Add --set flags for every trait

[atburke]

This PR adds a --set flag to tctl users update for every trait where it wasn't implemented already (Windows logins, Kube users/groups, DB users/names, and AWS role ARNs).

$ tctl users update \
--set-windows-logins winA,winB \
--set-kubernetes-users ku1 \
--set-kubernetes-groups kg1,kg2 \
--set-db-users a,b,c \
--set-db-names x,y,z \
--set-aws-role-arns foo,bar,baz andrew
User andrew has been updated:
	New database users: a,b,c
	New database names: x,y,z
	New AWS role ARNs: foo,bar,baz
	New Windows logins: winA,winB
	New Kubernetes users: ku1
	New Kubernetes groups: kg1,kg2

Part of #13783.

Closes #15083

[jakule]

Can you add some tests?

[alistanis]

Can you add some tests?

There isn't currently a lot of coverage for tctl users (at least it doesn't look like it at a glance) but there is a test file in tool/tctl/common/user_command_test.go. I would say take a look at how difficult adding tests for this is going to be; it'll require an IdentityService attached to a ClientI at a minimum I think, for which I'm not sure if we have mocks or not. If we don't already have mocks, maybe take a quick look at tool/tsh/tsh_test.go and look at invoking tctl directly instead and testing that?

[github-actions]

@atburke See the table below for backport results.

Branch	Result
branch/v10	Failed