resolve the errorprone warning.

[Liyixin95]

Resolve some of the errorprone warning, including ReferenceEquality, StringSplitter, and suppress the unchecked , rawtype and deprecation warning.
There are still two type of warning unresolved, including FunctionalInerfaceMethodChanged and FutureReturnValueIgnored.Should I suppress them or resolve them?

[codecov-io]

Codecov Report

Merging #862 into master will increase coverage by 0.01%.
The diff coverage is 87.5%.

@@             Coverage Diff              @@
##             master     #862      +/-   ##
============================================
+ Coverage     67.01%   67.02%   +0.01%     
- Complexity     1502     1503       +1     
============================================
  Files           146      146              
  Lines          7072     7072              
  Branches        901      901              
============================================
+ Hits           4739     4740       +1     
  Misses         1852     1852              
+ Partials        481      480       -1

Impacted Files	Coverage Δ	Complexity Δ
...eactor/netty/http/client/HttpClientOperations.java	64.22% <ø> (+0.29%)	71 <0> (+1)	⬆️
.../java/reactor/netty/channel/BootstrapHandlers.java	72.26% <ø> (ø)	40 <0> (ø)	⬇️
...ctor/netty/resources/PooledConnectionProvider.java	82.35% <ø> (ø)	27 <0> (ø)	⬇️
...c/main/java/reactor/netty/http/HttpOperations.java	73.21% <ø> (ø)	30 <0> (ø)	⬇️
src/main/java/reactor/netty/ReactorNetty.java	71.71% <ø> (ø)	43 <0> (ø)	⬇️
...a/reactor/netty/http/client/HttpClientConnect.java	58.26% <ø> (ø)	4 <0> (ø)	⬇️
.../main/java/reactor/netty/channel/MonoSendMany.java	63.88% <ø> (ø)	4 <0> (ø)	⬇️
...eactor/netty/channel/ChannelOperationsHandler.java	79.62% <0%> (ø)	11 <0> (ø)	⬇️
...or/netty/http/server/HttpServerMetricsHandler.java	72.41% <100%> (ø)	11 <1> (ø)	⬇️
...java/reactor/netty/http/server/ConnectionInfo.java	95.08% <100%> (ø)	25 <0> (ø)	⬇️
... and 4 more

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[violetagg]

thanks

[Liyixin95]

@violetagg What about the other two type of warning? Suppress or resolve? And I think the version of errorprone-gradle-plugin need to be update...

[violetagg]

I suppressed some of them and updated the plugin to version 0.8.1