[exporters/prometheus] Omit underscore suffix for unitless metrics #8517

Job	Run time
Bazel nortti	20m 10s
Bazel asan config	11m 11s
Bazel noexcept	18m 22s
Bazel on MacOS	29m 20s
Bazel	25m 44s
Bazel with async export	26m 59s
Bazel tsan config	20m 47s
Bazel valgrind	27m 45s
Bazel with external abseil	20m 25s
Benchmark	12m 54s
CMake test (with abseil)	6m 9s
CMake clang 14 (maintainer mode, async)	17m 26s
CMake clang 14 (maintainer mode, sync)	16m 47s
CMake do not install test (with otlp-exporter)	24m 56s
CMake gcc 4.8 (with otlp exporter)	16m 55s
CMake gcc 4.8 (without otlp exporter)	5m 51s
CMake gcc 12 (maintainer mode, async)	11m 5s
CMake gcc 12 (maintainer mode, C++11, async)	11m 9s
CMake gcc 12 (maintainer mode, sync)	10m 39s
CMake install test (with abseil)	6m 19s
CMake test (with modern protobuf,grpc and abseil)	41m 37s
CMake msvc (maintainer mode)	10m 18s
CMake test (with opentracing-shim)	6m 27s
CMake test (build shared libraries with otlp-exporter and static gRPC)	19m 49s
CMake test (with otlp-exporter)	20m 55s
CMake test (without otlp-exporter)	6m 47s
CMake C++20 test(Clang with libc++)	13m 26s
CMake C++20 test(GCC)	11m 45s
CMake test (without otlp-exporter and with async export)	6m 42s
Code coverage	13m 13s
Copyright	7s
DocFX check	1m 10s
Format	22s
markdown-lint	9s
misspell	9s
Plugin -> CMake	1m 21s
CMake -> exporter proto	16m 53s
Bazel Windows	37m 39s
Plugin -> CMake Windows	8m 59s
CMake (With async export) -> exporter proto	17m 39s
CMake -> exporter proto (Build as DLL)	16m 41s
	9h 53m 1s

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