feat: Allow adding VPC flow logs in environments

[KollaAdithya]

This PR solves #3721

• Added a flow_logs field to Environment manifest
• When the flow_logs is set to on then Cloud formation is going to create a FlowLog to capture information about the IP traffic going to and from network interfaces in your VPC.
• For Example, if the Environment Manifest contains

• Default VPC

network:
  vpc:
    flow_logs: on

• Imported VPC

network:
  vpc:
    id: 'vpc-12345'
    subnets:
      public:
        - id: 'subnet-11111'
        - id: 'subnet-22222'
      private:
        - id: 'subnet-33333'
        - id: 'subnet-44444’
    flow_logs: on

• Configured VPC

network:
  vpc:
      cidr: '10.0.0.0/16'
      subnets:
        public:
          - cidr: '10.0.0.0/24'
            az: 'us-east-2a'
          - cidr: '10.0.1.0/24'
            az: 'us-east-2b'
        private:
          - cidr: '10.0.3.0/24'
            az: 'us-east-2a'
          - cidr: '10.0.4.0/24'
            az: 'us-east-2b'
    flow_logs: on

• In all the cases with flow_logs: on creates a FlowLog with name AppName-EnvironmentName-FlowLogGroup that enables you to capture information about the IP traffic going to and from network interfaces in your VPC.
• It also creates an IAM Role to grant access for AWS EC2 to publish Flow logs to CloudWatch Logs.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the Apache 2.0 License.

[codecov-commenter]

Codecov Report

Merging #4088 (4cc8243) into mainline (08983f7) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##           mainline    #4088      +/-   ##
============================================
+ Coverage     69.16%   69.18%   +0.01%     
============================================
  Files           248      248              
  Lines         35606    35610       +4     
  Branches        264      264              
============================================
+ Hits          24628    24635       +7     
+ Misses         9783     9781       -2     
+ Partials       1195     1194       -1     

Impacted Files	Coverage Δ
internal/pkg/template/env.go	49.23% <ø> (ø)
internal/pkg/deploy/cloudformation/stack/env.go	72.04% <100.00%> (+0.08%)	⬆️
internal/pkg/manifest/env.go	78.76% <100.00%> (ø)
...ternal/pkg/deploy/cloudformation/cloudformation.go	72.47% <0.00%> (-0.55%)	⬇️
internal/pkg/manifest/storage.go	93.58% <0.00%> (ø)
internal/pkg/template/workload.go	42.58% <0.00%> (ø)
...al/pkg/deploy/cloudformation/stack/transformers.go	77.07% <0.00%> (+0.02%)	⬆️
internal/pkg/manifest/validate.go	84.17% <0.00%> (+0.08%)	⬆️
internal/pkg/aws/sessions/errors.go	33.33% <0.00%> (+7.24%)	⬆️

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[iamhopaul123]

Can we also add integ test for this feature at https://github.com/aws/copilot-cli/blob/b8c21b1023d0c6c8fe9aa22b1917183a42b2192e/internal/pkg/deploy/cloudformation/stack/env_integration_test.go ? Also could you add an example to the PR description for what the VPC flow logs look like?

[dannyrandall]

looks awesome!! just a couple of small things

[dannyrandall]