GH-128682: Account for escapes in DECREF_INPUTS

[markshannon]

This is the final PR (apart from potential bug fixes) for #128682.
It:

• Handles DECREF_INPUTS by either:
  • setting the on-stack references to NULL before closing them, or
  • where more efficient, setting the stack pointer before each reference is closed
• Changes many uses of DECREF_INPUTS to PyStackRef_CLOSE where there was only one input.
• Adds asserts that the stack pointer is spilled at key points outside of the interpreter.

• Issue: Consistently spill the evaluation stack when making escaping calls #128682

[iritkatriel]

Some tests are failing.

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @markshannon for commit 76001f7 🤖

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https://buildbot.python.org/all/#/grid?branch=refs%2Fpull%2F30617%2Fmerge

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[markshannon]

Latest benchmarking results show a 0.2% slowdown