Optimize `merge` algorithm for largest data sizes #213

Job	Run time
clang-format	10s
HOST,bknd=omp,cmplr=clang++,macos-latest,std=c++17,cfg=release	4m 15s
CPU,bknd=dpcpp,cmplr=icpx,ubuntu-latest,std=с++17,cfg=release	14m 24s
FPGA_EMU,bknd=dpcpp,cmplr=icpx,ubuntu-latest,std=с++17,cfg=release	14m 24s
HOST,bknd=tbb,cmplr=icx-cl,windows-latest,std=c++17,cfg=release	13m 47s
HOST,bknd=tbb,cmplr=icpx,ubuntu-latest,std=с++17,cfg=release	11m 45s
HOST,bknd=tbb,cmplr=cl,windows-latest,std=c++17,cfg=release	14m 10s
HOST,bknd=omp,cmplr=icpx,ubuntu-latest,std=с++17,cfg=release	9m 32s
CPU,bknd=dpcpp,cmplr=icx,windows-latest,std=c++17,cfg=release	11m 53s
HOST,bknd=omp,cmplr=g++,ubuntu-latest,std=с++17,cfg=release	5m 52s
HOST,bknd=tbb,cmplr=g++,ubuntu-latest,std=с++17,cfg=release	8m 51s
HOST,bknd=tbb,cmplr=g++,ubuntu-latest,std=с++17,cfg=release	8m 45s
HOST,bknd=tbb,cmplr=clang++,ubuntu-latest,std=с++17,cfg=release	11m 3s
HOST,bknd=omp,cmplr=clang++,ubuntu-latest,std=с++17,cfg=release	8m 5s
HOST,bknd=tbb,cmplr=clang++,ubuntu-latest,std=с++17,cfg=release	11m 2s
HOST,bknd=tbb,cmplr=icpx,ubuntu-latest,std=с++17,cfg=release	11m 52s
HOST,bknd=serial,cmplr=g++,ubuntu-latest,std=с++17,cfg=release	4m 51s
CPU,bknd=dpcpp,cmplr=icpx,ubuntu-latest,std=с++20,cfg=release	14m 24s
HOST,bknd=tbb,cmplr=icpx,ubuntu-latest,std=с++20,cfg=release	14m 19s
HOST,bknd=omp,cmplr=icpx,ubuntu-latest,std=с++20,cfg=release	14m 24s
	3h 27m 48s

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