Performance improvements

Instant-submission mode enabled by default when building with AdaptiveCpp

In GROMACS 2024, one had to manually enable the instant-submission mode of AdaptiveCpp when building GROMACS (-DSYCL_CXX_FLAGS_EXTRA=-DHIPSYCL_ALLOW_INSTANT_SUBMISSION=1). Now it is enabled by default, improving performance by up to 20% when running on GPU and slightly reducing the CPU usage when using SYCL/AdaptiveCpp backend.