Only initialize json marshaller when needed.

[anuraaga]

Bytecode generation can take a while during initialization and is pointless if it won't be needed. Client already had this check.

Fixes #1556

[codecov]

Codecov Report

Merging #1558 into master will decrease coverage by 0.05%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##             master    #1558      +/-   ##
============================================
- Coverage     72.76%   72.71%   -0.06%     
- Complexity     7281     7282       +1     
============================================
  Files           679      679              
  Lines         29379    29381       +2     
  Branches       3591     3591              
============================================
- Hits          21379    21364      -15     
- Misses         6138     6160      +22     
+ Partials       1862     1857       -5

Impacted Files	Coverage Δ	Complexity Δ
...inecorp/armeria/server/grpc/ArmeriaServerCall.java	83.2% <ø> (ø)	76 <0> (ø)	⬇️
.../com/linecorp/armeria/server/grpc/GrpcService.java	95.06% <100%> (+0.12%)	23 <2> (+1)	⬆️
.../linecorp/armeria/internal/Http1ObjectEncoder.java	62.92% <0%> (-11.22%)	43% <0%> (-5%)
...meria/internal/AbstractHttp2ConnectionHandler.java	83.33% <0%> (-6.67%)	11% <0%> (-1%)
...com/linecorp/armeria/internal/grpc/GrpcStatus.java	58.06% <0%> (-3.23%)	21% <0%> (-1%)
.../com/linecorp/armeria/server/docs/ServiceInfo.java	72.72% <0%> (-2.28%)	16% <0%> (-1%)
...common/stream/AbstractStreamMessageDuplicator.java	76.29% <0%> (-0.5%)	9% <0%> (ø)
...corp/armeria/common/logging/DefaultRequestLog.java	81.03% <0%> (+0.46%)	139% <0%> (+1%)	⬆️
.../armeria/internal/grpc/ArmeriaMessageDeframer.java	69.33% <0%> (+0.94%)	44% <0%> (+1%)	⬆️
.../linecorp/armeria/client/Http1ResponseDecoder.java	60% <0%> (+1.81%)	23% <0%> (+1%)	⬆️
... and 3 more

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[trustin]

Thanks @anuraaga!

[hyangtack]

Thanks!