[Cluster launcher] [aws] Bump max keys per account from 60 to 600

[architkulkarni]

Why are these changes needed?

Followup to #27506. This PR bumps it to 600.

Context from the previous PR copied below:

This is a minor QoL improvement to bump the hardcoded limit for number of aws keys per account. The limit is arbitrary and has been bumped before. AFAICT the fundamental aws limit is a 5000 key per region limit which we are not close to.

Related issue number

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[wuisawesome]

k i think we need to draw a hard limit at around 1k here since these keys are a global resource and we don't want to interfere with other applications.

btw i wonder if we should keep the default smaller and configure the constant via env var? I assume most users don't have a legitimate use case for so many keys.

[architkulkarni]

Oh good point, making it configurable via env var sounds good to me. Is the use case of a company account with many developers using the same account unusual? Maybe companies with >>5000 employees have multiple accounts. (5000 keys per region means 5000 keys per region per account, right?)

[wuisawesome]

I'm honestly not sure what the best practice is for that use case, but whatever the solution, I don't think that 5k key max is a quota that can easily be bumped.

[architkulkarni]

Failed test are unrelated. Will merge this for now. If we hit the limit again, we can make it configurable via env var or figure out another solution