[API] Create root span with active span (#2427) #8851

Job	Run time
CMake clang 14 (maintainer mode, sync)	14m 0s
CMake test (without otlp-exporter)	4m 53s
CMake test (with abseil)	4m 47s
CMake clang 14 (maintainer mode, abiv2)	13m 57s
CMake clang 14 (maintainer mode, async)	13m 53s
CMake gcc 12 (maintainer mode, async)	7m 33s
CMake gcc 12 (maintainer mode, sync)	8m 41s
CMake msvc (maintainer mode)	7m 40s
CMake test (with opentracing-shim)	4m 34s
CMake C++14 test(GCC)	4m 0s
CMake C++17 test(GCC)	4m 35s
CMake C++20 test(GCC)	8m 30s
CMake test (without otlp-exporter and with async export)	5m 4s
Bazel asan config	15m 17s
Bazel noexcept	12m 14s
Bazel nortti	12m 30s
Bazel on MacOS	26m 54s
Bazel	12m 45s
Bazel with async export	12m 36s
Bazel tsan config	13m 12s
Bazel valgrind	14m 24s
Bazel with external abseil	12m 51s
Benchmark	8m 15s
CMake do not install test (with otlp-exporter)	13m 57s
CMake install test (with abseil)	4m 31s
CMake test (with modern protobuf,grpc and abseil)	18m 15s
CMake test (build shared libraries with otlp-exporter and static gRPC)	13m 34s
CMake test (with otlp-exporter)	13m 59s
CMake C++20 test(Clang with libc++)	9m 25s
Code coverage	11m 41s
Copyright	7s
DocFX check	1m 4s
Format	15s
markdown-lint	7s
misspell	4s
Plugin -> CMake	1m 6s
CMake -> exporter proto	12m 54s
Bazel Windows	23m 33s
Plugin -> CMake Windows	7m 8s
CMake (With async export) -> exporter proto	12m 29s
CMake -> exporter proto (Build as DLL)	12m 15s
	6h 39m 29s

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