Remove grpc-gateway dependency

[yurishkuro]

Which problem is this PR solving?

• Part of Define internal version of OTLP proto types using Gogo optimizations #5052
• Continues Add manual implementation of APIv3 HTTP endpoints #5054
• Closes Remove dependency on deprecated github.com/golang/protobuf #4911

Description of the changes

• Replace grpc-gateway based implementation with manual HTTP implementation from Add manual implementation of APIv3 HTTP endpoints #5054
• Clean up spurious grpc-gateway usage (e.g. all-in-one test that did not need it)
• Delete grpc-gateway step from make proto and remove the corresponding generated file
• go mod tidy removes grpc-gateway and github.com/golang/protobuf

How was this change tested?

• CI

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (718f666) 52.59% compared to head (f2b93b7) 95.60%.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #5060       +/-   ##
===========================================
+ Coverage   52.59%   95.60%   +43.00%     
===========================================
  Files         145      313      +168     
  Lines        8599    18292     +9693     
===========================================
+ Hits         4523    17488    +12965     
+ Misses       3728      644     -3084     
+ Partials      348      160      -188     

Flag	Coverage Δ
cassandra-3.x	25.61% <ø> (ø)
cassandra-4.x	25.61% <ø> (ø)
elasticsearch-5.x	19.88% <ø> (ø)
elasticsearch-6.x	19.88% <ø> (+0.01%)	⬆️
elasticsearch-7.x	20.02% <ø> (ø)
elasticsearch-8.x	20.11% <ø> (+0.01%)	⬆️
grpc-badger	19.50% <ø> (ø)
kafka	14.10% <ø> (ø)
opensearch-1.x	20.00% <ø> (-0.02%)	⬇️
opensearch-2.x	20.02% <ø> (ø)
unittests	93.28% <100.00%> (?)

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[yurishkuro]

renamed from grpc_gateway_test.go