Use 5.0.0+trunk name and version

[shakthimaan]

• Use 5.0.0 name and version for all +trunk and +stable variant builds.
• The dependencies/packages/ocaml-base-compiler/ocaml-base-compiler.5.00.0+trunk has been cleaned up.
• All scripts and CI have been updated to use this new versioning number.

[shakthimaan]

The domainslib.0.4.2 update builds fine now. Tested with:

make clean
TAG='"macro_bench"' make multicore_parallel_run_config_filtered.json
TAG='"macro_bench"' make multicore_parallel_run_config_filtered_filtered.json
make multicore_parallel_run_config_filtered_filtered_2domains.json
USE_SYS_DUNE_HACK=1 BUILD_BENCH_TARGET=multibench_parallel \
  RUN_CONFIG_JSON=multicore_parallel_run_config_filtered_filtered_2domains.json \
  make ocaml-versions/5.0.0+trunk.bench