[improve][broker] Replace all ConcurrentOpenHashMap with the official ConcurrentHashMap in JDK

[BewareMyPower]

Motivation

See #23215

Modifications

For broker related modules, including pulsar-broker, pulsar-websocket, managed-ledger,

• Replace all ConcurrentOpenHashMap<T> with ConcurrentHashMap<T>
• Replace all ConcurrentOpenHashSet<T> fields with ConcurrentHashMap<T, Boolean>
• Replace unnecessary reflections in tests
• Remove ConcurrentOpenHashSet since it's never used now

Documentation

• doc
• doc-required
• doc-not-needed
• doc-complete

Matching PR in forked repository

PR in forked repository: BewareMyPower#34

[ocadaruma]

Hi, the change looks make sense.
For ConcurrentOpenHashSet, how about replacing type declarations with Set and use ConcurrentHashMap.newKeySet() ?

To express the Set type, it's more straightforward than ConcurrentHashMap<T, Boolean> and helps the reader IMO.

[BewareMyPower]

declarations with Set and use ConcurrentHashMap.newKeySet() ?

Good suggestion. I will adopt this suggestion.

BTW, I will split this PR into multiple parts because of there are many changes. So let me mark it drafted now and push more PRs.