XProc runtime for XSpec

[wendellpiez]

User Story:

It would be very fine to be able to run XSpec tests with the same infrastructure as we use for other production pipelines.

It is also essential to enable others to run our tests and to integrate them into CI/CD (and see #1).

XSpec already has XProc 1.0 infrastructure which we could adapt.

Both writing HTML reports, and bundling XSpecs with 'blind' reporting, would potentially be useful capabilities from the command line.

Goals:

Two XProc demonstrations and a bash script:

• An XProc that runs a single XSpec, producing its native and HTML results on its output ports
• A shell script to call XML Calabash under Maven, to run this on an XSpec instance
• An XProc that runs a sequence of XSpecs, collecting their (pre-rendering) results and filtering those to provide summary outputs

Since we can also call Calabash directly from within make maybe we can forgo a script for the bundler XProc.

Dependencies:

The repository already has examples of calling XML Calabash to execute XProc 1.0 pipelines under Maven, with scripts to do so.

The XProc foundations are in the XSpec module - support/xspec/src/harnesses/saxon/saxon-xslt-harness.xproc

Acceptance Criteria

• All website and readme documentation affected by the changes in this issue have been updated. Changes to the website can be made in the docs/content directory of your branch.
• A Pull Request (PR) is submitted that fully addresses the goals of this User Story. This issue is referenced in the PR.
• The CI-CD build process runs without any reported errors on the PR. This can be confirmed by reviewing that all checks have passed in the PR.

[wendellpiez]

Now complete, with extras, and closeable with final push thanks to @aj-stein-nist