[feat][admin] Add offload managedLedgerOffloadThreshold RestAPI and CLI tools

[tjiuming]

Motivation

Add offload managedLedgerOffloadThreshold RestAPI and CLI tools

Does this pull request potentially affect one of the following parts:

If the box was checked, please highlight the changes

• 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
• Anything that affects deployment

Documentation

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

Matching PR in forked repository

PR in forked repository: tjiuming#8

[codecov-commenter]

Codecov Report

Merging #18218 (77b8032) into master (aeb4503) will increase coverage by 15.86%.
The diff coverage is 76.19%.

@@              Coverage Diff              @@
##             master   #18218       +/-   ##
=============================================
+ Coverage     31.39%   47.26%   +15.86%     
- Complexity     6651    10465     +3814     
=============================================
  Files           697      697               
  Lines         68015    68058       +43     
  Branches       7285     7286        +1     
=============================================
+ Hits          21353    32166    +10813     
+ Misses        43667    32311    -11356     
- Partials       2995     3581      +586     

Flag	Coverage Δ
unittests	47.26% <76.19%> (+15.86%)	⬆️

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

Impacted Files	Coverage Δ
.../org/apache/pulsar/broker/admin/v2/Namespaces.java	59.74% <71.42%> (+50.40%)	⬆️
...pache/pulsar/broker/admin/impl/NamespacesBase.java	64.13% <80.95%> (+51.94%)	⬆️
...java/org/apache/pulsar/proxy/stats/TopicStats.java	58.82% <0.00%> (-41.18%)	⬇️
...apache/pulsar/client/impl/AutoClusterFailover.java	73.33% <0.00%> (-2.78%)	⬇️
...a/org/apache/pulsar/proxy/server/ProxyService.java	80.00% <0.00%> (-0.94%)	⬇️
...che/bookkeeper/mledger/impl/ManagedCursorImpl.java	37.11% <0.00%> (-0.06%)	⬇️
.../apache/pulsar/broker/namespace/LookupOptions.java	87.50% <0.00%> (ø)
...che/bookkeeper/mledger/impl/ManagedLedgerImpl.java	53.86% <0.00%> (+0.02%)	⬆️
.../pulsar/client/impl/ProducerStatsRecorderImpl.java	84.66% <0.00%> (+0.61%)	⬆️
...va/org/apache/pulsar/client/impl/ProducerImpl.java	17.01% <0.00%> (+1.16%)	⬆️
... and 165 more

[tjiuming]

/pulsarbot run-failure-checks