[Release cycle] Consider shifting release cycle to align with Python’s annual release schedule

### Describe the enhancement requested

Currently, PyArrow/Arrow releases tend to happen around the same time as new Python releases, which creates a timing challenge where PyArrow support for new Python versions arrives after the Python stable release rather than before it.

### Current situation

Python releases its ABI-stable release candidate in late July each year, while Arrow’s feature freeze typically occurs in early October. This timing results in PyArrow supporting new Python versions approximately 1 month after Python’s stable release, making PyArrow often the last dependency in the ecosystem to support new Python versions.

### Proposal

We could shift the Arrow release cycle to better align with Python’s annual schedule. Specifically, since Python’s ABI-stable RC arrives in late July (for example, Python 3.15 will be July 28, 2026), we could move the Arrow feature freeze to early August (around August 1st), then take the usual time to resolve blockers and release in late August or early September.

This would position PyArrow to support new Python versions approximately 1 month before Python’s stable release instead of 1 month after, ensuring PyArrow wheels are available when or shortly after new Python versions are released.

### Benefits and considerations

This change would reduce pressure on downstream packages that depend on PyArrow and provide better alignment with the Python ecosystem’s needs. The timing would become more predictable for Python version support planning.

However, Arrow is a multi-language project, and the release schedule needs to balance requirements across all components including C++, Java, Go, R, and others.

### Context

This suggestion originated from discussion in issue #47438 regarding Python 3.14 support.

### Component(s)

Packaging, Release, Integration