Backport of [ui] Namespace added to example test in exec window into release/1.7.x

[hc-github-team-nomad-core]

Backport

This PR is auto-generated from #20218 to be assessed for backporting due to the inclusion of the label backport/1.7.x.

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The person who merged in the original PR is:
@philrenaud
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/nomad/merges: 409 Merge conflict []

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

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Adds a -namespace $NAMESPACEID string to the example we show when you exec in a task in the Nomad web UI (when not in the default namespace)

Resolves #20213

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Overview of commits

• fee242c

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1 out of 2 committers have signed the CLA.

• philrenaud
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[github-actions]

Ember Test Audit comparison

	release/1.7.x	e8e6660	change
passes	1548	1549	+1
failures	0	0	0
flaky	0	0	0
duration	10m 30s 826ms	10m 29s 356ms	-01s 470ms

[github-actions]

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