Add optional 'escape routes' to proxied VPC terraform examples

[abyrne55]

This PR adds optional "escape routes" to the proxied VPC terraform scripts under examples/aws/terraform/. I used this to test the --no-proxy feature added in #280. This feature allows us to simulate customer networks that have NO_PROXY routes to external services (e.g., splunk).

Checklist

• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have tested the functionality against gcp / aws, it doesn't cause any regression
• I have added execution results to the PR's readme

How to test this PR locally / Special Instructions

Follow the instructions in both READMEs, and be sure to set a value for the proxied_subnet_escape_routes variable in your terraform.tfvars. If you use the provided bash one-liner to get all the Splunk IPs, you'll be able to run the verifier on the proxied subnet (using the instructions in the READMEs, incl. the bit about downloading the CA cert) and pass all checks, even for Splunk.

[openshift-ci]

Skipping CI for Draft Pull Request.
If you want CI signal for your change, please convert it to an actual PR.
You can still manually trigger a test run with /test all

[openshift-ci]

@abyrne55: all tests passed!

Full PR test history. Your PR dashboard.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository. I understand the commands that are listed here.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 25.79%. Comparing base (d86f9d5) to head (edf1453).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #281      +/-   ##
==========================================
- Coverage   25.91%   25.79%   -0.12%     
==========================================
  Files          25       26       +1     
  Lines        1837     1845       +8     
==========================================
  Hits          476      476              
- Misses       1333     1341       +8     
  Partials       28       28              

see 4 files with indirect coverage changes

[joshbranham]

/lgtm

[abyrne55]

/approve

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: abyrne55, joshbranham

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [abyrne55]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment