[fix][broker] Fix thread-safety issue with currentLedgerEntries and currentLedgerSize fields

[lhotari]

Motivation

• currentLedgerEntries and currentLedgerSize fields in the ManagedLedgerImpl class are currently mutated and read from multiple threads which is a problem.
  • one solution is to make the fields volatile

Modifications

• make fields volatile

Documentation

• [ ] doc-required (Your PR needs to update docs and you will update later)

• [x] doc-not-needed (Please explain why)

• [ ] doc (Your PR contains doc changes)

• [ ] doc-complete (Docs have been already added)

Matching PR in forked repository

PR in forked repository: https://github.com/lhotari/pulsar/pull/93

[lhotari]

I noticed this while working on #17252

[github-actions[bot]]

The pr had no activity for 30 days, mark with Stale label.

[codecov-commenter]

Codecov Report

Merging #17868 (fdff41a) into master (22866bd) will decrease coverage by 10.02%. The diff coverage is 100.00%.

@@              Coverage Diff              @@
##             master   #17868       +/-   ##
=============================================
- Coverage     45.92%   35.90%   -10.03%     
+ Complexity    10104     7754     -2350     
=============================================
  Files           680      706       +26     
  Lines         66758    69004     +2246     
  Branches       7147     7392      +245     
=============================================
- Hits          30660    24776     -5884     
- Misses        32680    40894     +8214     
+ Partials       3418     3334       -84     

Flag	Coverage Δ
unittests	35.90% <100.00%> (-10.03%)	:arrow_down:

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...va/org/apache/pulsar/broker/service/ServerCnx.java	48.19% <ø> (-2.26%)	:arrow_down:
.../java/org/apache/pulsar/client/impl/ClientCnx.java	29.97% <ø> (ø)
...org/apache/pulsar/proxy/server/ProxyClientCnx.java	46.51% <ø> (ø)
...rg/apache/pulsar/proxy/server/ProxyConnection.java	55.21% <ø> (ø)
...che/bookkeeper/mledger/impl/ManagedLedgerImpl.java	53.81% <100.00%> (+0.04%)	:arrow_up:
...ava/org/apache/pulsar/broker/admin/v1/Brokers.java	0.00% <0.00%> (-100.00%)	:arrow_down:
...va/org/apache/pulsar/broker/admin/v1/Clusters.java	0.00% <0.00%> (-100.00%)	:arrow_down:
.../org/apache/pulsar/broker/admin/v1/Properties.java	0.00% <0.00%> (-100.00%)	:arrow_down:
.../apache/pulsar/broker/admin/v2/ResourceGroups.java	0.00% <0.00%> (-100.00%)	:arrow_down:
...ar/common/naming/PartitionedManagedLedgerInfo.java	0.00% <0.00%> (-100.00%)	:arrow_down:
... and 158 more