SYCL NBNXM kernels

Testing caveats:

• Increased timeout for unit tests with SYCL build to 480 seconds.
• Increased tolerance for Exact Continuation test with BD integrator to 500 ULP (was already bumped twice in the past year, first from 64 to 128, and later to 200).
• Only OpenCL backend (SYCL_BE=PI_OPENCL) was tested, due to a lock-up in LevelZero. The fix is merged, but not yet a part of an official release.

Unit and regression tests confirmed to pass (except position-restraints, see #3846 (closed)) on the following configurations (2021-02-03, dc54de23):

• local desktop (GPU HD 530 (Gen9), OneAPI 2021.1.2, IGC 1.0.6083, Compute Runtime 21.04.18912),
• local laptop (GPU Xe G7 (Gen12), OneAPI 2021.1.2, IGC 1.0.6083, Compute Runtime 21.04.18912),
• intel-gpu01 (GPU UHD P630 (gen9.5), OneAPI 2021.1.1, IGC 1.0.5723, Compute Runtime 20.49.18626),
• • To use this intel-compute-runtime, please do MODULEPATH=/nethome/aland/modules/modulefiles:$MODULEPATH module load intel-compute-runtime/20.49.18626,
• intel-gpu02 (GPU DG1 (Gen12), OneAPI 2021.1.1, Compute Runtime 21.03),
• • Even position-restraints passes fine,
• • A patch to zero-initialize plist is needed (!1065 (merged)).

Performance differs from OpenCL but is on-par. Not including precise error estimations here, but the variation over multiple runs seems to be less than the difference between platforms. Best time in bold.

rnase-cubic, mdrun -ntmpi 1 -ntomp 4 -nb gpu -pme cpu -resethway -nsteps 5000 -nobackup -gpu_id X, reported ns/day.

HW	SYCL (OpenCL)	SYCL (L0)	OpenCL
Xe G7	80.6	94.5	85.1
UHD P630	34.0	N/A	38.2
HD 530	27.9	30.9	30.5

rnase-cubic, mdrun -ntmpi 2 -ntomp 2 -nb gpu -pme cpu -resethway -nsteps 5000 -nobackup -gpu_id X, reported ns/day.

HW	SYCL (OpenCL)	OpenCL
Xe G7	45.9	36.2
UHD P630	26.5	30.4
HD 530	19.6	24.3