fix: Add enable_data_source_optimizations variable

[boost-ben]

Description

This PR addresses a regression introduced in v21.0.0 where the terraform-aws-eks module became incompatible with depends_on, breaking existing v20 user configurations with 'Invalid count argument' errors.

Rather than force some users to refactor their working infrastructure (without a migration path) for optimization gains they may not need, it gives users the choice to reduce the number of GET requests for partition and account_id across submodules.

Motivation and Context

Resolves #3440

Breaking Changes

No

How Has This Been Tested?

• I have updated at least one of the examples/* to demonstrate and validate my change(s)
• I have tested and validated these changes using one or more of the provided examples/* projects
  Tested with examples/eks-managed-node-group
• I have executed pre-commit run -a on my pull request

[bryantbiggs]

again, this is not a valid change, nor will it solve the "problem" you are claiming

the authors of the language state that you should not do this hashicorp/terraform#30340 (comment)

[andreiboost]

I understand using depends_on is (heavily) discouraged, this whole situation reminds me of https://xkcd.com/1172/. However the truth is that something like this PR does fix planning when depends_on is used on the EKS module.

Would you consider approving a PR making the two datasources optional, by adding var.partition and var.account_id?

[github-actions]

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