Split sycl_iterator tests to separate tests

[SergeyKopienko]

In this PR we split sycl_iterator tests to separate tests: one test in one file. The goal - to avoid timeout errors in CI system for these tests.

Configuration	Label Time Summary (main branch)	Label Time Summary (this branch)
CPU,bknd=dpcpp,cmplr=icpx,ubuntu-20.04,std=с++17,cfg=release	209.17 sec*proc (7 tests)	224.53 sec*proc (78 tests)
FPGA_EMU,bknd=dpcpp,cmplr=icpx,ubuntu-20.04,std=с++17,cfg=release	58.60 sec*proc (7 tests)	63.56 sec*proc (78 tests)
HOST,bknd=tbb,cmplr=icpx,ubuntu-20.04,std=с++17,cfg=release	Total Test time (real) = 56.33 sec	Total Test time (real) = 56.64 sec
HOST,bknd=tbb,cmplr=icpx,ubuntu-20.04,std=с++17,cfg=release	Total Test time (real) = 55.94 sec	Total Test time (real) = 56.23 sec
HOST,bknd=omp,cmplr=icpx,ubuntu-20.04,std=с++17,cfg=release	Total Test time (real) = 59.84 sec	Total Test time (real) = 59.84 sec
...	...	...
CPU,bknd=dpcpp,cmplr=icx,windows-2019,std=c++17,cfg=release	254.18 sec*proc (7 tests)	317.38 sec*proc (78 tests)

This info has been collected from https://github.com/oneapi-src/oneDPL/actions/runs/9764889560 and from https://github.com/oneapi-src/oneDPL/actions/runs/9778104870?pr=1660

UPD: after applying the PR https://github.com/oneapi-src/oneDPL/pull/1667 from Julian, probably this PR isn't required anymore. But may be somebody know another reasons to apply it?