[EXPORTER] Change OTLP HTTP content_type default to binary #9001

Job	Run time
CMake clang 14 (maintainer mode, async)	13m 11s
CMake gcc 12 (maintainer mode, async)	7m 24s
CMake clang 14 (maintainer mode, sync)	14m 7s
CMake gcc 12 (maintainer mode, sync)	8m 21s
CMake test (without otlp-exporter)	5m 35s
CMake clang 14 (maintainer mode, abiv2)	12m 55s
CMake test (with abseil)	5m 3s
CMake msvc (maintainer mode)	8m 30s
CMake msvc (maintainer mode) with C++20	8m 53s
CMake test (with opentracing-shim)	4m 54s
CMake C++14 test(GCC)	4m 8s
CMake test (without otlp-exporter and with async export)	4m 46s
Bazel	11m 31s
Bazel with async export	11m 36s
Bazel with external abseil	12m 5s
CMake do not install test (with otlp-exporter)	13m 19s
CMake install test (with abseil)	4m 59s
CMake test (with modern protobuf,grpc and abseil)	18m 57s
CMake test (build shared libraries with otlp-exporter and static gRPC)	13m 13s
CMake test (with otlp-exporter)	13m 57s
CMake C++17 test(GCC)	4m 50s
CMake C++20 test(Clang with libc++)	9m 17s
CMake C++20 test(GCC)	8m 9s
Plugin -> CMake	2m 0s
Bazel asan config	14m 35s
Bazel noexcept	11m 11s
Bazel nortti	11m 37s
Bazel on MacOS	16m 21s
Bazel tsan config	12m 33s
Bazel valgrind	11m 53s
Benchmark	8m 29s
Copyright	4s
Format	20s
CMake -> exporter proto	12m 44s
Bazel Windows	22m 18s
CMake (With async export) -> exporter proto	12m 20s
CMake -> exporter proto (Build as DLL)	12m 54s
Code coverage	11m 21s
DocFX check	51s
markdown-lint	5s
misspell	3s
Plugin -> CMake Windows	6m 46s
	6h 28m 5s

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