aws: allow setting max retries from AWS_MAX_ATTEMPTS env var

[grosser]

Which component this PR applies to?

cluster-autoscaler

What type of PR is this?

/kind feature

What this PR does / why we need it:

atm aws fails after 3 retries since we use the default config, which leads to backoffs, which leads to clusters not scaling as requested

Does this PR introduce a user-facing change?

- support AWS_MAX_ATTEMPTS to configure max retries

[gjtempleton]

/assign @gjtempleton

Hey there @grosser, thanks for the PR!

Apologies, hadn't noticed this one before so there's now a merge conflict post the merging of #5120 to address as well as the comment on variable naming styling from the PR check. If you get those addressed happy to get this merged as agreed on this looking useful.

[grosser]

rebased, lmk if that looks good :)

[gjtempleton]

One more small request, can we add a brief entry to the AWS cloudprovider readme to explain how to make use of this?

Other than that, this LGTM.

[grosser]

done

[grosser]

@gjtempleton

[gjtempleton]

Thanks!
/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: gjtempleton, grosser

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