Query AWS to find subnets with explicitely specified subnet IDs

[codablock]

What type of PR is this?
/kind feature

What this PR does / why we need it:
This basically unifies the code used to find subnets with filters and subnets
by ID. This is done by handling the ID case as a simple filter instead of
looking into the cluster network spec.

The reason is that explicitely specified subnets are not necessarely part
of the cluster network spec. For example, it might be desired to run a
EKS control plane inside 3 specific subnets (so they are part of the
network spec) while running workers in different subnets from the same
VPC.

A side effect of this change is that we don't have to check for the correct
failure domain and/or public/private subnets anymore as this is implicitely
handled by the criterias.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

Special notes for your reviewer:

Checklist:

• squashed commits
• includes documentation
• adds unit tests
• adds or updates e2e tests

Release note:

Allow to specify subnets by ID which are not part of the cluster's network spec

[k8s-ci-robot]

Hi @codablock. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[randomvariable]

Thanks for this. I'm sure you're right, but I need have a think about it, as ever, with any of the networking code.

[randomvariable]

Still not had time to review this. Will look on monday.

In the meantime,

/ok-to-test

[codablock]

FYI, the note about not requiring to check for AZ/publicIPS that I made in the initial commit and in the PR description is not really true anymore. One commit later I decided to re-add comparable checks to the filter code so that error messages are more useful. Always being to told that a subnet does not exist when in reality it simply doesn't match the AZ/IP criteria ist very confusing.

[enxebre]

This make sense to me.
Another example where this is natural is externally managed infrastructure. I see this decoupling as a good thing.

[codablock]

@randomvariable Sorry to bother you, but did you find time to look into this? :)

[enxebre]

cc @richardcase @sedefsavas for awareness, any objections to proceed with this?

[richardcase]

cc @richardcase @sedefsavas for awareness, any objections to proceed with this?

Will take a look @enxebre

[codablock]

@pydctw @sedefsavas Thanks for your reviews :)
I've rebased on main, fixed the last nit and squashed commits. Hopefully ready to merge now.

[pydctw]

/lgtm

[sedefsavas]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: sedefsavas

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