chore(e2e): update e2e tests to use t.Context()

[wongtonyb]

Description

This PR updates the e2e tests to use t.Context() in replacement for context.Background() for the testing portion of the test.

t.Context() is ideal for the test execution portion, as it will auto cancel the context at the end of the test (on successful completion, failure, or timeout), but before any t.Cleanup functions.

Clean up functions, as well as any other functions that require explicit control over when to cancel (ie. goroutines) is required to use a new context with context.Background()

Jira Ticket: https://hashicorp.atlassian.net/browse/ICU-17222

PCI review checklist

• I have documented a clear reason for, and description of, the change I am making.
• If applicable, I've documented a plan to revert these changes if they require more than reverting the pull request.
• If applicable, I've documented the impact of any changes to security controls.
  Examples of changes to security controls include using new access control methods, adding or removing logging pipelines, etc.

[irenarindos]

Looks good, though make-gen-delta is complaining with a formatting nit:
https://github.com/hashicorp/boundary/actions/runs/20756965352/job/59601550353?pr=6316

[moduli]

Looks good, though make-gen-delta is complaining with a formatting nit: https://github.com/hashicorp/boundary/actions/runs/20756965352/job/59601550353?pr=6316

@irenarindos I think this was fixed in bo's pr that addresses flaky unit tests. @wongtonyb if you rebase with main, this should get resolved.