[fix][broker][branch-2.8] Fix potential to add duplicated consumer

[poorbarcode]

Motivation

see #15051

There have conflicts when cherry-picking #15051 PR (branch 2.8 has no mock static support), so I created a separate PR to fix branch-2.8

Modifications

Swap the execution order of duplicate validation and maximum validation

Documentation

• doc-required

• doc-not-needed

• doc

• doc-complete

[poorbarcode]

@BewareMyPower Could you take a look?

[poorbarcode]

/pulsarbot rerun-failure-checks

[poorbarcode]

/pulsarbot rerun-failure-checks

[BewareMyPower]

We can merge this PR once only CI - Unit / unit-tests (pull_request) failed because there is a broken test, see #16813.

[poorbarcode]

/pulsarbot rerun-failure-checks

[BewareMyPower]

Merge this PR first, it looks like NamespacesTest.testDeleteNamespaceWithBundles is also very flaky.

Wanted but not invoked:
asyncResponse.resume(<Capturing argument>);
-> at org.apache.pulsar.broker.admin.NamespacesTest.testDeleteNamespaceWithBundles(NamespacesTest.java:859)

However, there was exactly 1 interaction with this mock:
asyncResponse.resume(
    org.apache.pulsar.broker.web.RestException: Failed to find ownership for ServiceUnit:my-tenant/use/test-delete-namespace-with-bundles/0x00000000_0x80000000
);
-> at org.apache.pulsar.broker.web.PulsarWebResource.resumeAsyncResponseExceptionally(PulsarWebResource.java:1226)