Backport of [NET-5163] Support locality testing in consul-container into release/1.16.x

[hc-github-team-consul-core]

Backport

This PR is auto-generated from #18484 to be assessed for backporting due to the inclusion of the label backport/1.16.

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The person who merged in the original PR is:
@zalimeni
This person should manually cherry-pick the original PR into a new backport PR,
and close this one when the manual backport PR is merged in.

merge conflict error: POST https://api.github.com/repos/hashicorp/consul/merges: 409 Merge conflict []

The below text is copied from the body of the original PR.

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• Support including locality in client sidecar config.
• Refactor fortio test helpers to separate HTTP retries from waiting on fortio result changes due to e.g. service startup and failovers.
• Align test config structs with Ent to avoid future conflicts.

I was planning to backport the non-locality changes further back, but there's other divergence that complicates doing that, so just doing 1.16 for now.

Note: these changes are primarily to support Ent testing in a separate change

PR Checklist

• updated test coverage
• external facing docs updated
• appropriate backport labels added
• not a security concern

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Overview of commits

• 716dd11 - e75311f

[hashicorp-cla]

All committers have signed the CLA.

[github-team-consul-core-pr-approver]

Auto approved Consul Bot automated PR