Add new .pmgrc.yaml setting PMG_VASP_PSP_SUB_DIRS: dict[str, str]

[janosh]

the current PotcarSingle.functional_dir hard-codes the subfolder structure of PMG_VASP_PSP_DIR. e.g. the subfolder containing the PBE_64 POTCARs must be named POT_PAW_PBE_64. this causes problems e.g. in cases where the POTCARs are shared across an HPC cluster and users don't have permissions to rename shared files (just happened to me).

pymatgen/pymatgen/io/vasp/inputs.py

Lines 1757 to 1779 in 232fa1f

	# We indicate the older release in `functional_dir` as PBE_52, PBE_54, LDA_52, LDA_54.
	# The newer release is indicated as PBE_52_W_HASH, etc.
	functional_dir: ClassVar = {
	"PBE": "POT_GGA_PAW_PBE",
	"PBE_52": "POT_GGA_PAW_PBE_52",
	"PBE_52_W_HASH": "POTPAW_PBE_52",
	"PBE_54": "POT_GGA_PAW_PBE_54",
	"PBE_54_W_HASH": "POTPAW_PBE_54",
	"PBE_64": "POT_PAW_PBE_64",
	"LDA": "POT_LDA_PAW",
	"LDA_52": "POT_LDA_PAW_52",
	"LDA_52_W_HASH": "POTPAW_LDA_52",
	"LDA_54": "POT_LDA_PAW_54",
	"LDA_54_W_HASH": "POTPAW_LDA_54",
	"LDA_64": "POT_LDA_PAW_64",
	"PW91": "POT_GGA_PAW_PW91",
	"LDA_US": "POT_LDA_US",
	"PW91_US": "POT_GGA_US_PW91",
	"Perdew_Zunger81": "POT_LDA_PAW",
	}
	functional_tags: ClassVar = {
	"pe": {"name": "PBE", "class": "GGA"},

the new setting is read from .pmgrc.yaml and overrides the PotcarSingle.functional_dir names (leaving unspecified ones as is). example:

# .pmgrc.yaml
PMG_VASP_PSP_DIR: /path/to/pseudo-potentials
PMG_VASP_PSP_SUB_DIRS:
  PBE_64: MY_PBE_64_DIR
  LDA_64: MY_LDA_64_DIR

this PR implement the new setting, adds tests for it and restores (uncomments) + fixes an existing PotcarSingle test
also improves FileNotFoundError messages on missing POTCARs

[janosh]

pinging @esoteric-ephemera since i can't request a review from you but would be great to get your thoughts if any

[mkhorton]

Seems reasonable to me. I am not familiar with the W_HASH variants.

[esoteric-ephemera]

This looks good to me! This can also benefit those who are newer to VASP and only care about more recent generations of pseudopotentials.

@mkhorton: afaik, these are identical to the non _W_HASH variants ({PBE,LDA}_52, {PBE,LDA}_54) but with a SHA and possibly COPYR field added.