fix: update number of route tables in intra subnets to match num AZs

[megashby]

Description

Create one route table and associated route table association per subnet for intra subnets

Motivation and Context

We need to deploy lambdas in a VPC that has both private subnet and intra subnet tiers. Our use case is some lambdas will need to be able to connect to the internet via NATGWs, but some lambdas won't need any outbound internet access. For lambdas that will be deployed in the intra subnets, they will be in multiple AZs and the current pattern of only having one route table shared amongst all subnets is not compatible with patterns like having VPC endpoints / private link endpoints deployed in all subnets.

Breaking Changes

No, outputs for intra_subnets_route_table_ids and intra_subnets_route_table_association_ids will now potentially have more than 1 output.

How Has This Been Tested?

• [ x ] I have updated at least one of the examples/* to demonstrate and validate my change(s)
• [ x ] I have tested and validated these changes using one or more of the provided examples/* projects

Running complete and separate-route-tables examples show that 3 route tables are now being created.

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

[github-actions]

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