Create ElementWrapper.find and ElementWrapper.findall

[pressler-vsc]

Description

Credit to @mtrachy

This PR adds find and findall methods to ElementWrapper, which should significantly improve the UX for CPHD/CRSD-esque identifier-based element lookups.

Examples from UG

>>> wrappedsicd["ImageFormation"].find("Processing", Type="inscription")
ElementWrapper({'Type': 'inscription', 'Applied': True, 'Parameter': (('krange', 'fixed'), ('kazimuth', 'fixed'))})
 >>> wrappedsicd["ImageFormation"].find("Processing", Applied=True)
ElementWrapper({'Type': 'inscription', 'Applied': True, 'Parameter': (('krange', 'fixed'), ('kazimuth', 'fixed'))})
 >>> wrappedsicd["ImageFormation"].find("Processing", Applied=False) is None
True