feat: Add support for multiple route tables to public and intra subnets

[KevinSnyderCodes]

Description

Support for multiple route tables when creating public and intra subnets.

Motivation and Context

Guarantee that the used route table for public and intra subnets on creation is different when a boolean variable is set to true.

• Resolves #1020

Breaking Changes

No breaking changes, as the variables are optional and defaulted to false.

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
• [x] I have executed pre-commit run -a on my pull request

  Changes were tested in a staging environment where existing public and intra subnets and route tables existed. Multiple route tables were enabled for both public and intra subnets. The existing route tables and associations were successfully updated and network traffic continued to flow as normal.

[KevinSnyderCodes]

@bryantbiggs Any interest in introducing this feature to the module? I'm happy to update the examples and finalize this PR if this is something you'd be open to merging.

[Smana]

tf-controller plan output:

No changes. Your infrastructure matches the configuration.

Terraform has compared your real infrastructure against your configuration
and found no differences, so no changes are needed.

To apply this plan, please merge this pull request.

[adubkov]

Any movements on this? Would love to have it.

[antonbabenko]

This PR is included in version 5.8.0 :tada:

[github-actions[bot]]

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