Fix wxPython 4.2 / wxWidgets 3.2 compatibility (resolves macOS 14+ crash)

[jdlondon]

Problem

The Cecilia5 5.4.1 download on the project page crashes immediately
after the splash screen on macOS 14 (Sonoma) and later with a segfault
inside libwx_osx_cocoau_core-3.1.4.0.0.dylib during
CGFunctionEvaluate. A native crash report shows the offending call is
in the CGShading callback
(wxMacCoreGraphicsPenBrushDataBase::CalculateShadingValues), which
receives a NULL info pointer on Sonoma's deferred display-list
renderer. The crash triggers on any gradient brush, and the Cecilia UI
uses gradients heavily (sliders, knobs, toggles, label triangles), so
it has no way to proceed. wxWidgets 3.2 handles the lifecycle
correctly.

Rebuilding against wxPython 4.2 / wxWidgets 3.2 avoids the crash but
exposes wxPython 4.2's stricter type checking for drawing-method
arguments (floats no longer silently coerced to int). Most such sites
were fixed on master by the 2021–2023 commits (655954e, 266d613,
14a27ef, 8e97a59), but a handful remain. Additionally,
wx.GraphicsContext_Create (underscored alias) was removed in
wxPython 4.2 and needs the dotted form.

Fixes (5 commits, each self-contained)

1. Fix remaining float values in wxPython 4.2 drawing calls.
   13 call sites across CeciliaPlot.py, Sliders.py, Widgets.py,
   Control.py where Python 3 true division or arithmetic on float
   attributes produced floats. Fixed in place with int(...) wrappers
   or // division, matching the style established in commits
   14a27ef and 8e97a59. Includes the
   wx.Colour(knobcolor[0] * 0.25, ...) case at Sliders.py:1484,
   which parallels the * 0.35 fix already applied to the sibling
   RangeSlider.setFillColour on master.

2. Replace wx.GraphicsContext_Create with wx.GraphicsContext.Create.
   26 occurrences across 5 files. The underscored alias was removed in
   wxPython 4.2; the dotted form has been available for many versions
   and is backwards-compatible.

3. py2app: include pyo explicitly. pyo is imported
   conditionally in audio.py (pyo64 vs pyo based on sample precision),
   so py2app's static analyser misses it and omits it from the bundle.

4. info.plist: target Python 3.11. Updates PyRuntimeLocations,
   PythonExecutable, and version strings from Python 2.7 stubs to
   3.11.

5. builder_OSX.sh: target Python 3.11 / wxWidgets 3.2. Bumps
   install_name_tool paths from 3.1.4.0.0 → 3.2.0.4.2 dylibs and
   python3.7 → python3.11. Also fixes broken find -exec syntax
   (missing semicolons on the .git/.pyc cleanup lines) and narrows
   the hidden-file cleanup to only .DS_Store so it doesn't also
   strip .gitignore, __pycache__, etc. Adds a post-build step that
   flattens py2app's Contents/Resources/Resources/ nesting, because
   constants.py expects RESOURCES_PATH == Contents/Resources.

Testing

Built against Python 3.11.12 / wxPython 4.2.5 / wxWidgets 3.2.9 on
macOS 14.8.3. Verified with the bundled .app:

• Default startup (random module): 30s runtime, zero errors.
• AutoModFilter (range widget; previously crashed with
  NoneType.slider downstream from a wx.Colour(float) in
  buildGrapher): loads cleanly.
• MultiBandDelay (csplitter path, exercises the Sliders.py:1484
  fix): loads cleanly.
• One module from every category (Dynamics / Filters / Multiband /
  Pitch / Resonators&Verbs / Spectral / Synthesis / Time): all load
  cleanly.

Note on the binary release

I notice that the 5.4.1 version on the project site predates the more
recent drawing fixes, and the official macOS binary has the wx crash
on Sonoma and later. Hopefully the fixes in this PR are helpful if
you're considering a future updated release. I've left the version in
the builder script at 5.4.1 for now.

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AI usage disclosure: some parts of this PR and its summary were
prepared and validated using Opus 4.6 and 4.7.