add PARSL_MPI_PREFIX as prefix #12497

Job	Run time
tests-defects-phonons-espresso	4m 50s
tests-engines (dask)	4m 26s
tests-core (3.9, ubuntu-latest)	4m 56s
tests-engines (parsl)	2m 27s
tests-core (3.12, ubuntu-latest)	3m 42s
tests-engines2 (prefect)	2m 10s
tests-engines (redun)	1m 52s
tests-core (3.12, windows-latest)	4m 43s
tests-engines (jobflow)	42s
tests-engines-covalent	8m 27s
tests-mlps	2m 7s
tests-psi4	1m 42s
tests-qchem-sella	3m 33s
tests-tblite-dftbplus	2m 45s
codecov	12s
	48m 34s

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