[type:refactor] optimize the performance of MemoryLimitCalculator#maxAvailable

[loongs-zhang]

this PR optimize the performance of MemoryLimitCalculator#maxAvailable.

[codecov-commenter]

Codecov Report

Merging #3316 (d45b849) into master (dfd5cb3) will decrease coverage by 0.05%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##             master    #3316      +/-   ##
============================================
- Coverage     64.40%   64.35%   -0.06%     
+ Complexity     5178     5175       -3     
============================================
  Files           742      742              
  Lines         20957    20964       +7     
  Branches       1919     1919              
============================================
- Hits          13498    13491       -7     
- Misses         6183     6193      +10     
- Partials       1276     1280       +4     

Impacted Files	Coverage Δ
...henyu/common/concurrent/MemoryLimitCalculator.java	66.66% <100.00%> (+29.16%)	⬆️
...yu/sync/data/http/refresh/AbstractDataRefresh.java	70.00% <0.00%> (-13.34%)	⬇️
...che/shenyu/sync/data/http/HttpSyncDataService.java	77.23% <0.00%> (-6.51%)	⬇️
...henyu/admin/service/impl/UpstreamCheckService.java	70.14% <0.00%> (-1.50%)	⬇️
...he/shenyu/plugin/logging/AbstractLogCollector.java
...e/shenyu/plugin/logging/LoggingRocketMQPlugin.java
...gin/logging/rocketmq/RocketMQLogCollectClient.java
...shenyu/plugin/logging/entity/ShenyuRequestLog.java
.../apache/shenyu/plugin/logging/sampler/Sampler.java
...he/shenyu/plugin/logging/sampler/CountSampler.java
... and 30 more

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