Make pNFS block easier to deploy

[chucklever]

I would like to see more deployment of XFS with block layout. This needs to be ready for the pNFS with NVMe extension.

However, currently there is little documentation for this, and none of what exists is fresh or easily findable. The troubleshooting messages are not understandable by administrators. Setting up iSCSI is difficult. We also have no regular testing of this deployment scenario.

Therefore, we want:

• CI testing per kernel release with all the usual workloads
• Better observability (convert dprintk sites to trace points)
• Up-to-date deployment recipes
• Better fallback behavior during misconfiguration or network partition

[chucklever]

I've constructed a framework within kdevops that can provision an iSCSI system and set up an XFS export with pNFS enabled. Specific Kconfig options for pNFS block have been added to the gitr, pynfs, and fstests workflows.