Backport of E2E: test enforcement of ACL system into release/1.5.x

[hc-github-team-nomad-core]

Backport

This PR is auto-generated from #16796 to be assessed for backporting due to the inclusion of the label backport/1.5.x.

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

---

Follow-up to #16775
Closes #16483

This changeset provides a matrix test of ACL enforcement across several dimensions:

• anonymous vs bogus vs valid tokens
• permitted vs not permitted by policy
• request sent to server vs sent to client (and forwarded)

In order for this test to be meaningful for anonymous requests, I also had to reduce the permissions of the anonymous policy on the E2E cluster. The test runner uses a management token unless there's a test that overrides it that I've missed. I've spot-checked this didn't cause any new breakage on E2E tests but we have a few things like #16803 floating around that make it hard to be sure without digging into all the existing failures we need to work thru.

---

Test against Nomad 1.5.2, showing how this would have caught #16775:

$ go test -v -count=1 ./auth
=== RUN   TestAuth
=== RUN   TestAuth/AnonServerRequests
=== RUN   TestAuth/BogusServerRequests
=== RUN   TestAuth/InvalidPermissionsServerRequests
=== RUN   TestAuth/ValidPermissionsServerRequests
=== RUN   TestAuth/AnonClientRequests
    assert.go:11:
        auth_test.go:208: expected non-nil error; is nil
        ↪ PostScript | annotation ↷
                expected error when reading namespace
=== RUN   TestAuth/BogusClientRequests
=== RUN   TestAuth/InvalidPermissionsClientRequests
=== RUN   TestAuth/ValidPermissionsClientRequests
--- FAIL: TestAuth (0.22s)
    --- PASS: TestAuth/AnonServerRequests (0.00s)
    --- PASS: TestAuth/BogusServerRequests (0.01s)
    --- PASS: TestAuth/InvalidPermissionsServerRequests (0.01s)
    --- PASS: TestAuth/ValidPermissionsServerRequests (0.02s)
    --- FAIL: TestAuth/AnonClientRequests (0.00s)
    --- PASS: TestAuth/BogusClientRequests (0.01s)
    --- PASS: TestAuth/InvalidPermissionsClientRequests (0.01s)
    --- PASS: TestAuth/ValidPermissionsClientRequests (0.01s)
FAIL
FAIL    github.com/hashicorp/nomad/e2e/auth     0.230s
FAIL

Test against 1.5.3:

$ go test -v -count=1 ./auth
=== RUN   TestAuth
=== RUN   TestAuth/AnonServerRequests
=== RUN   TestAuth/BogusServerRequests
=== RUN   TestAuth/InvalidPermissionsServerRequests
=== RUN   TestAuth/ValidPermissionsServerRequests
=== RUN   TestAuth/AnonClientRequests
=== RUN   TestAuth/BogusClientRequests
=== RUN   TestAuth/InvalidPermissionsClientRequests
=== RUN   TestAuth/ValidPermissionsClientRequests
--- PASS: TestAuth (1.41s)
    --- PASS: TestAuth/AnonServerRequests (0.12s)
    --- PASS: TestAuth/BogusServerRequests (0.08s)
    --- PASS: TestAuth/InvalidPermissionsServerRequests (0.11s)
    --- PASS: TestAuth/ValidPermissionsServerRequests (0.14s)
    --- PASS: TestAuth/AnonClientRequests (0.13s)
    --- PASS: TestAuth/BogusClientRequests (0.14s)
    --- PASS: TestAuth/InvalidPermissionsClientRequests (0.17s)
    --- PASS: TestAuth/ValidPermissionsClientRequests (0.19s)
PASS
ok      github.com/hashicorp/nomad/e2e/auth     1.422s