docs: validate and update E2E test docs

[bm54cloud]

Description

This PR aims to:

• Update dependencies required in E2E testing docs
• Clarify Kubernetes cluster configuration needed for E2E testing
• Reduce tribal knowledge by validating the testing E2E testing docs are correct and identify/correct any knowledge gaps in the documentation

Related Issue

Relates to #2477

Checklist before merging

• Test, docs, adr added or updated as needed
• Contributor Guide Steps followed

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[bm54cloud]

@brandtkeller @AustinAbro321 Can I get some early feedback on the //Verify cluster connectivity section I added in 20_zarf_init_test.go. Originally was trying to work in main_test.go to verify cluster, but skipK8sEnvVar did not work as I expected it to. I left my original thought process in main_test.go commented out. This is what the error in 20_zarf_init_test.go would look like, so it would fail early. More so just wondering if putting it in 20_zarf_init_test.go is good or if you would truly prefer it in main_test.go.

[brandtkeller]

@brandtkeller @AustinAbro321 Can I get some early feedback on the //Verify cluster connectivity section I added in 20_zarf_init_test.go. Originally was trying to work in main_test.go to verify cluster, but skipK8sEnvVar did not work as I expected it to. I left my original thought process in main_test.go commented out. This is what the error in 20_zarf_init_test.go would look like, so it would fail early. More so just wondering if putting it in 20_zarf_init_test.go is good or if you would truly prefer it in main_test.go.

This is a great fallback but I would love to hear more about what limitations or constraints you ran into regarding main_test.go (this doesn't have to be the location/solution if we deem an appropriate solution is something along what you have currently - but I do want to capture notes).

I would point out that the current solution is limited to specific test commands. The out of the box test-e2e would likely run through all non-cluster e2e tests before failing and any filter of cluster e2e tests that run while not using 20_ would also not be covered.