PCI: Parse units for physical size

[dgault]

This is a follow up to the original PR https://github.com/ome/bioformats/pull/3880

Comparing the data repo updates to the equivalent HCImage data suggests that the magnification value should not be used for physical size when the units are Pixels. https://github.com/openmicroscopy/data_repo_config/pull/539

This may mean further repo updates if there are other datasets with pixel units.

[melissalinkert]

Code changes make sense to me, I think this is fine to merge once configuration issues are sorted out and tests are confirmed to pass.

[dgault]

Quite a few failures in the repo tests due to adding the units to the physical size, most of this are likely correct updates but some such as Length: value[0.054921], unit[pixel] look odd and will require a manual review of each update. https://merge-ci.openmicroscopy.org/jenkins/job/BIOFORMATS-test-folder/lastFailedBuild/console

As such I suggest we fix the values for this release and follow up with the units addition for a later release to give more time for review.

[dgault]

Merge CI is now green without the unit changes. Getting this merged for 6.11.0 and we can follow up on the units addition for the next release