[Python/EC2] Add pipeline exporter for custom metrics testing

[Miqueasher]

This PR adds the 'Custom export pipeline' to the existing Python E2E test.
Changes include:

1. Addition of custom export pipeline according to public docs here.
2. Update to validation templates to include pipeline custom metrics
3. Update to env. variables to export test id number.

A git revert back to the last passing CSHA: fb173f2 .

Ensure you've run the following tests on your changes and include the link below:

To do so, create a test.yml file with name: Test and workflow description to test your changes, then remove the file for your PR. Link your test run in your PR description. This process is a short term solution while we work on creating a staging environment for testing.

Test 1
Test 2
Test 3

NOTE: TESTS RUNNING ON A SINGLE EKS CLUSTER CANNOT BE RUN IN PARALLEL. See the needs keyword to run tests in succession.

• Run Java EKS on e2e-playground in us-east-1 and eu-central-2
• Run Python EKS on e2e-playground in us-east-1 and eu-central-2
• Run metric limiter on EKS cluster e2e-playground in us-east-1 and eu-central-2
• Run EC2 tests in all regions
• Run K8s on a separate K8s cluster (check IAD test account for master node endpoints; these will change as we create and destroy clusters for OS patching)

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.