[improve][ml] Avoid acquire ManagedLedgerImpl synchronized lock when cursor init finished.

[lifepuzzlefun]

Motivation

since ManagedCursorContainer is threadsafe. so it is not unnecessary to try to hold synchronized lock when cursor init finished.

Modifications

1. change HashMap uninitializedCursors to ConcurrentHashMap
2. remove acquire unnecessary synchronized lock

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• Dependencies (add or upgrade a dependency)
• The public API
• The schema
• The default values of configurations
• The threading model
• The binary protocol
• The REST endpoints
• The admin CLI options
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• Anything that affects deployment

Documentation

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