[Doc] Add doc on how to configure max subscriptions per topic at the topic level

[Jennifer88huang-zz]

Master Issue: #8866
Related PR: #8948

Motivation

In #8948, we support configuring max subscriptions at topic level.

Modifications

1. Add related doc content for this feature.
2. Fix some minor typos.

[Jennifer88huang-zz]

@315157973 we might need to add related options for set-max-subscriptions if we have. Could you provide available options? Thank you.

[315157973]

It looks good, but I have some questions:
What does tenant/namespace/topic mean?

If we use this command,a topic name should be passed in here, such as:
persistent://tenant/namespace/topic

The entire command looks like this:
pulsar-admin topics set-max-subscriptions [topic name] [options]

[315157973]

Now this command is also called get-max-subscriptions-per-topic at topic-level. But I think it would be more reasonable to call get-max-subscriptions. I will post a PR to fix this problem later.
Because, we have get-max-producers-per-topic at namespace-level, but it is called get-max-producers at topic-level. We should be consistent with these rules.

[315157973]

Here is the PR #9750

[Anonymitaet]

Need to add them to pulsar-admin website? or is set-max-subscriptions same to set-max-subscriptions-per-topic? Same comments for the other two commands.

[Jennifer88huang-zz]

set-max-subscriptions is the same to set-max-subscriptions-per-topic, fixed in PR #9750

[Jennifer88huang-zz]

@315157973 @Anonymitaet updated, PTAL again, thank you.

[Jennifer88huang-zz]

@315157973 @codelipenghui if there is no further issue, could you approve and merge it? If you have any concern, feel free to comment. Thank you.