flow control: refactor and group dependencies in FlowController constructor

[evacchi]

What type of PR is this?

/kind cleanup

What this PR does / why we need it:
Follow-up to @LukeAVanDrie's suggestion in #2530 (comment)

Refactor controller.NewFlowController() to accept a controller.Deps{} struct with the expected parameters. This also makes the opts varargs probably less useful, so this PR proposes to remove that too.

Notice error checking is pretty minimal, i.e. we only default the clock to a RealClock when the field is nil, otherwise we assume the rest of the parameters are correct. I can add more error checking if it's more consistent with the rest of the codebase.

Which issue(s) this PR fixes:
Fixes #2764

Does this PR introduce a user-facing change?:

NONE

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[k8s-ci-robot]

Hi @evacchi. Thanks for your PR.

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[LukeAVanDrie]

/lgtm

Notice error checking is pretty minimal, i.e. we only default the clock to a RealClock when the field is nil, otherwise we assume the rest of the parameters are correct. I can add more error checking if it's more consistent with the rest of the codebase.

Since we control all callers here, this is fine. I didn't want unnecessary defensive checks. Though, this is usually more of a concern for anything running on the hot path.

[ahg-g]

/ok-to-test

[evacchi]

/retest

(possibly a flake)

[ahg-g]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ahg-g, evacchi

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