Forward declarations of host dispatch tags #8211

Job	Run time
clang-format	28s
codespell	19s
PSTL offload cpu,bknd=dpcpp,cmplr=icpx,ubuntu-22.04,std=с++17,cfg=release	11m 35s
documentation	26s
HOST,bknd=omp,cmplr=icpc,macos-11,std=c++17,cfg=release	36m 11s
HOST,bknd=tbb,cmplr=icx-cl,windows-2019,std=c++17,cfg=release	19m 37s
CPU,bknd=dpcpp,cmplr=icpx,ubuntu-20.04,std=с++17,cfg=release	14m 23s
HOST,bknd=tbb,cmplr=cl,windows-2019,std=c++17,cfg=release	15m 41s
CPU,bknd=dpcpp,cmplr=icx,windows-2019,std=c++17,cfg=release	15m 53s
FPGA_EMU,bknd=dpcpp,cmplr=icpx,ubuntu-20.04,std=с++17,cfg=release	15m 43s
HOST,bknd=tbb,cmplr=icpx,ubuntu-20.04,std=с++17,cfg=release	13m 1s
HOST,bknd=omp,cmplr=icpx,ubuntu-20.04,std=с++17,cfg=release	10m 53s
HOST,bknd=omp,cmplr=g++,ubuntu-latest,std=с++17,cfg=release	6m 36s
HOST,bknd=tbb,cmplr=g++,ubuntu-latest,std=с++17,cfg=release	9m 53s
HOST,bknd=tbb,cmplr=g++,ubuntu-20.04,std=с++17,cfg=release	11m 37s
HOST,bknd=tbb,cmplr=clang++,ubuntu-20.04,std=с++17,cfg=release	11m 29s
HOST,bknd=omp,cmplr=clang++,ubuntu-20.04,std=с++17,cfg=release	7m 55s
HOST,bknd=tbb,cmplr=clang++,ubuntu-latest,std=с++17,cfg=release	13m 0s
HOST,bknd=tbb,cmplr=icpx,ubuntu-20.04,std=с++17,cfg=release	12m 57s
HOST,bknd=serial,cmplr=g++,ubuntu-20.04,std=с++17,cfg=release	5m 37s
	3h 53m 14s

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