fix #1641, support get system load on windows

[diecui1202]

What is the purpose of the change

fix #1641, support get system load on windows

Brief changelog

XXXXX

Verifying this change

XXXXX

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[codecov-io]

Codecov Report

Merging #2631 into master will decrease coverage by 0.08%.
The diff coverage is 0%.

@@             Coverage Diff              @@
##             master    #2631      +/-   ##
============================================
- Coverage     55.16%   55.07%   -0.09%     
+ Complexity     5293     5287       -6     
============================================
  Files           571      571              
  Lines         25521    25524       +3     
  Branches       4532     4533       +1     
============================================
- Hits          14078    14057      -21     
- Misses         9338     9357      +19     
- Partials       2105     2110       +5

Impacted Files	Coverage Δ	Complexity Δ
...dubbo/common/status/support/LoadStatusChecker.java	46.15% <0%> (-13.85%)	2 <0> (ø)
...onfig/spring/extension/SpringExtensionFactory.java	75.86% <0%> (-10.35%)	11% <0%> (ø)
...he/dubbo/remoting/transport/netty/NettyClient.java	72.88% <0%> (-10.17%)	12% <0%> (-1%)
...e/dubbo/remoting/transport/netty/NettyChannel.java	57.5% <0%> (-8.75%)	19% <0%> (-2%)
...ubbo/rpc/protocol/dubbo/ChannelWrappedInvoker.java	41.66% <0%> (-4.17%)	3% <0%> (ø)
...rpc/protocol/dubbo/telnet/InvokeTelnetHandler.java	54.21% <0%> (-3.62%)	13% <0%> (-2%)
...dubbo/rpc/protocol/dubbo/CallbackServiceCodec.java	77.2% <0%> (-1.48%)	29% <0%> (ø)
.../dubbo/remoting/transport/netty4/NettyChannel.java	61.17% <0%> (-1.18%)	22% <0%> (-1%)
...apache/dubbo/rpc/protocol/dubbo/DubboProtocol.java	58.33% <0%> (-0.84%)	30% <0%> (-1%)
.../java/org/apache/dubbo/config/ReferenceConfig.java	50.71% <0%> (+1.07%)	42% <0%> (ø)	⬇️
... and 1 more

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