[software] Add message-passing messagep_fp16 kernel #2109

Job	Run time
check-control-registers	19s
check-opcodes	3s
riscv-isa-sim	7s
tc-gcc	24s
tc-llvm	51s
verilator	12s
verilator-model (minpool)	12s
verilator-model (mempool)	7s
check-bootrom	13s
build-apps-gcc (minpool)	51s
build-apps-gcc (mempool)	52s
tc-halide	11s
build-apps-llvm (minpool)	50s
build-apps-llvm (mempool)	49s
unit-test	2m 30s
build-apps-halide (minpool)	43s
build-apps-halide (mempool)	1m 13s
run-apps-gcc	0s
run-apps-llvm	0s
run-apps-halide (minpool)	42s
run-apps-halide (mempool)	3m 14s
clean-up-compile-runs (minpool)	5s
clean-up	3s
clean-up-compile-runs (mempool)	3s
	14m 34s

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