Reuse time metadata config in XIOS

[jwallwork23]

Use model config in XIOS

Fixes #925
Follows #936
Second attempt following #932
Merges into #913

Task List

• Defined the tests that specify a complete and functioning change (It may help to create a design specification & test specification)
• Implemented the source code change that satisfies the tests
• Documented the feature by providing worked example
• Updated the README or other documentation
• Completed the pre-Request checklist below

---

Change Description

This PR reuses the time metadata set as part of the config set in the XIOS handler.

---

Test Description

For the purposes of testing, a separate Model.configureTime member function is created to avoid having to configure everything. I also needed to get the build system to create partition metadata files for 1 and 3 MPI ranks for the XIOS tests and to extend the configuration for all of them.

---

Documentation Impact

The XIOS doc pages are updated to reflect these changes.

---

Pre-Request Checklist

• The requirements of this pull request are fully captured in an issue or design specification and are linked and summarised in the description of this PR
• No new warnings are generated
• The documentation has been updated (or an issue has been created to track the corresponding change)
• Methods and Tests are commented such that they can be understood without having to obtain additional context
• This PR/Issue is labelled as a bug/feature/enhancement/breaking change
• This change conforms to the conventions described in the README

[timspainNERSC]

I think you could use metadata.runLength() in one place, but otherwise this looks good.

[timspainNERSC]

Isn't metadata.runLength() exactly metadata.stopTime() - metadata.startTime()? (It should be)

[jwallwork23]

Good point, thanks @timspainNERSC. Addressed in 326c552.