Avoid `if` call in the `__parallel_merge_submitter_large::run_parallel_merge()` #269

Job	Run time
clang-format	14s
HOST,bknd=omp,cmplr=clang++,macos-latest,std=c++17,cfg=release	4m 13s
HOST,bknd=tbb,cmplr=icx-cl,windows-latest,std=c++17,cfg=release	5m 31s
CPU,bknd=dpcpp,cmplr=icpx,ubuntu-latest,std=с++17,cfg=release	1m 19s
HOST,bknd=tbb,cmplr=cl,windows-latest,std=c++17,cfg=release	5m 33s
FPGA_EMU,bknd=dpcpp,cmplr=icpx,ubuntu-latest,std=с++17,cfg=release	1m 36s
CPU,bknd=dpcpp,cmplr=icx,windows-latest,std=c++17,cfg=release	4m 15s
HOST,bknd=tbb,cmplr=icpx,ubuntu-latest,std=с++17,cfg=release	4m 47s
HOST,bknd=omp,cmplr=icpx,ubuntu-latest,std=с++17,cfg=release	2m 56s
HOST,bknd=omp,cmplr=g++,ubuntu-latest,std=с++17,cfg=release	5m 28s
HOST,bknd=tbb,cmplr=g++,ubuntu-latest,std=с++17,cfg=release	5m 47s
HOST,bknd=tbb,cmplr=g++,ubuntu-latest,std=с++17,cfg=release	5m 47s
HOST,bknd=tbb,cmplr=clang++,ubuntu-latest,std=с++17,cfg=release	5m 47s
HOST,bknd=omp,cmplr=clang++,ubuntu-latest,std=с++17,cfg=release	5m 47s
HOST,bknd=tbb,cmplr=clang++,ubuntu-latest,std=с++17,cfg=release	5m 46s
HOST,bknd=tbb,cmplr=icpx,ubuntu-latest,std=с++17,cfg=release	2m 57s
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	26s
HOST,bknd=tbb,cmplr=icpx,ubuntu-latest,std=с++20,cfg=release	1s
HOST,bknd=omp,cmplr=icpx,ubuntu-latest,std=с++20,cfg=release	1m 22s
	1h 14m 23s

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