api: Expose vSphere API to evict subscribed content library

Closes: #3400

Description

This change exposes the vSphere API to evict the subscribed content library to free up storage capacity. The vSphere API evicts the cached content of an on-demand subscribed library. This operation allows the cached content of a subscribed library to be removed to free up storage capacity. This operation will only work when a subscribed library is synchronized on-demand.

Closes: #3400

Type of change

Please mark options that are relevant:

[ ] Bug fix (non-breaking change which fixes an issue)
[x] New feature (non-breaking change which adds functionality)
[ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
[ ] This change requires a documentation update
[ ] Build related change

How Has This Been Tested?

Ran the govc tests locally

acharyasreej@acharyasreY5WYK test % ./library.bats library.bats ✓ library ✓ library.import ✓ library.deploy ✓ library.clone ovf ✓ library.deploy vmtx ✓ library.vmtx.info ✓ library.pubsub ✓ library.subscriber example ✓ library.create.withpolicy ✓ library.findbyid ✓ library.trust ✓ library.session ✓ library.probe ✓ library.evict

Checklist:

[x] My code follows the CONTRIBUTION guidelines of this project
[ ] I have commented my code, particularly in hard-to-understand areas
[ ] I have made corresponding changes to the documentation
[x] I have added tests that prove my fix is effective or that my feature works
[ ] New and existing unit tests pass locally with my changes
[ ] Any dependent changes have been merged

vmware / govmomi