display_timing: expose via Config and CLI (#290)

[DLWoodruff]

Summary

• Fixes display_timing should be in config.py #290. display_timing was a "secret menu" option that callers had to set on the options dict by hand. Move it into mpisppy.utils.config.Config next to display_progress and display_convergence_detail so it shows up under --help and propagates through cfg_vanilla the same way.
• shared_options() now forwards cfg.display_timing into the hub's opt_kwargs.options.
• subgradient_spoke, ph_dual_spoke, relaxed_ph_spoke hardcode options["display_timing"] = False, matching the existing pattern for the other two display flags (spokes should not print per-iteration diagnostics).
• doc/src/secretmenu.rst: drop the display_timing section now that it's a first-class CLI option. The other two secret-menu entries (initial_proximal_cut_count, subgradient_while_waiting) remain.
• doc/src/hubs.rst: mention the new --display-timing flag next to the existing --with-display-convergence-detail note so the option stays discoverable from the docs.
• phbase.py:887-888 keeps its defensive default so PHBase can still be instantiated outside the cfg flow.

Test plan

• ruff check clean on changed files
• Config().popular_args(); cfg.display_timing works and defaults to False
• New unit tests in mpisppy/tests/test_ef_ph.py::Test_sizes:
  • test_display_timing_emits_nonzero_solve_times runs PH iter0 with display_timing=True, captures stdout, asserts the "Pyomo solve times (seconds):" header appears, parses the min/mean/max stats line, and requires max > 0. Guards against a future refactor quietly dropping the option from self.options or the print path.
  • test_display_timing_off_suppresses_solve_times confirms the timing report is not printed when the flag is False, so the assertion above isn't catching unconditionally-emitted output.
• CLI smoke test: examples/run_all.py now appends --display-timing to the existing sizes/sizes_cylinders.py run, so the run_all.py CI jobs exercise the new flag end-to-end through generic_cylinders.py-style invocation.
• Generic cylinders integration: confirmed mpisppy/generic/parsing.py:120 calls cfg.popular_args(), so --display-timing automatically appears on python -m mpisppy.generic_cylinders --module-name ... --help with no additional wiring.
• CI run on this PR

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[codecov]

Codecov Report

❌ Patch coverage is 75.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 71.42%. Comparing base (bbe8fba) to head (27c6eac).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
mpisppy/utils/cfg_vanilla.py	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #708      +/-   ##
==========================================
+ Coverage   71.28%   71.42%   +0.13%     
==========================================
  Files         154      154              
  Lines       19438    19462      +24     
==========================================
+ Hits        13857    13901      +44     
+ Misses       5581     5561      -20     

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