bridge: Switch to using the libpcp units parsing interface
bridge: Switch to using the libpcp units parsing interface

Remove the out-of-date copy of pmParseUnitsStr from the PCP
bridge, and switch to the interface libpcp has provides for
over 3 years now.  This seems safe to do now, as Cockpit has
dependencies on slightly more recent versions of PCP than
that in other areas (e.g. via use of PM_VERSION macro).

This removes the final open-coded __pm-routine (libpcp) use,
such that Cockpit uses only official, supported, documented
PMAPI routines now.

Closes #8764

stefwalter/cockpit,cockpituous/cockpit,garrett/cockpit,deryni/cockpit,stefwalter/cockpit,SotolitoLabs/cockpit,moraleslazaro/cockpit,mareklibra/cockpit,moraleslazaro/cockpit,deryni/cockpit,stefwalter/cockpit,martinpitt/cockpit,moraleslazaro/cockpit,cockpit-project/cockpit,garrett/cockpit,moraleslazaro/cockpit,garrett/cockpit,mvollmer/cockpit,martinpitt/cockpit,andreasn/cockpit,deryni/cockpit,mvollmer/cockpit,mvollmer/cockpit,mareklibra/cockpit,mareklibra/cockpit,SotolitoLabs/cockpit,cockpituous/cockpit,cockpituous/cockpit,andreasn/cockpit,SotolitoLabs/cockpit,SotolitoLabs/cockpit,andreasn/cockpit,cockpituous/cockpit,stefwalter/cockpit,mvollmer/cockpit,stefwalter/cockpit,stefwalter/cockpit,andreasn/cockpit,moraleslazaro/cockpit,SotolitoLabs/cockpit,deryni/cockpit,stefwalter/cockpit,cockpit-project/cockpit,mvollmer/cockpit,SotolitoLabs/cockpit,garrett/cockpit,cockpituous/cockpit,cockpituous/cockpit,cockpit-project/cockpit,martinpitt/cockpit,deryni/cockpit,cockpit-project/cockpit,mareklibra/cockpit,andreasn/cockpit,mareklibra/cockpit,martinpitt/cockpit,andreasn/cockpit,moraleslazaro/cockpit,martinpitt/cockpit,garrett/cockpit,SotolitoLabs/cockpit,mareklibra/cockpit,deryni/cockpit,deryni/cockpit,cockpit-project/cockpit,mareklibra/cockpit,moraleslazaro/cockpit,andreasn/cockpit