Add EXCL_STRIDE to XML PE configs

[amametjanov]

This enables selection of custom EXCL_STRIDE values from
config_pesall.xml PE files to populate $case-dir/env_mach_pes.xml: e.g.

  <grid ...>
    <mach name="pm-gpu">
      <pes compset=...>
        <ntasks>
          ...
        </ntasks>
        <pstrid>
          <pstrid_atm>16</pstrid_atm>
        </pstrid>
        <excl_stride>
          <excl_stride_atm>16</excl_stride_atm>
        </excl_stride>
      </pes>
    </mach>
  </grid>

Checklist

• My code follows the style guidlines of this proejct (black formatting)
• I have performed a self-review of my own code
• My changes generate no new warnings
• I have added tests that excerise my feature/fix and existing tests continue to pass
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding additions and changes to the documentation

[github-actions]

You can preview documentation at https://esmci.github.io/cime/branch/azamat/pes/add-xstrid-to-xml/html/index.html

[jedwards4b]

I'm having trouble understanding what new functionality this provides? Can't we already specify this with the existing xml variables?

[amametjanov]

Previously, I couldn't set excl_stride for a matching grid+compset+mach as in this config_pesall.xml file when matching a _PS modifier in

./cime/scripts/create_test SMS_PS.ne256pg2_r025_RRSwISC6to18E3r5.WCYCLXX2010.pm-gpu_gnugpu

I tried black formatting, but GH-CI black hook is still failing. Not sure how to get it passing:

> black --version
black, 25.9.0 (compiled: yes)
Python (CPython) 3.11.7

> black CIME/case/case.py
All done! ✨ 🍰 ✨
1 file left unchanged.

> black CIME/XML/pes.py
All done! ✨ 🍰 ✨
1 file left unchanged.

[rljacob]

@jasonb5 can you help get this passing the black formatter?

[jgfouca]

@jedwards4b , you did not approve when you looked at this back in October. Can you take a second look?