Modernize CI: new Go versions, C23 fix, Windows testing

[b-long]

This PR consolidates 6 stacked changes that modernize the CI pipeline and fix
compatibility issues with newer compilers and Go versions.

Summary of changes

• Modernize GitHub Actions — upgrade all actions to current versions, pin
  Python to 3.11, remove AppVeyor, skip two known-broken CGO tests
• Enable CI on stacked/feature branches — pull_request trigger now runs
  on PRs targeting any branch, not just master
• Expand Go version matrix — add Go 1.24.x and 1.25.x to CI
• Fix C23 compiler compatibility — guard typedef uint8_t bool; against
  C23's native bool to fix build errors with newer C compilers
• Update golang.org/x/tools — bump from v0.16.0 → v0.29.0, required for
  Go 1.25.x compatibility
• Resume Windows CI — re-enable Windows runner, fix LF line-ending issue
  that broke TestCheckSupportMatrix, add Windows test docs

---

[1/6] Update GitHub Actions and skip failing CGO tests — #382

Changes:

• Remove appveyor.yml
• Upgrade actions/checkout v2 → v4
• Upgrade actions/setup-go v2 → v5 (with built-in caching, removes separate cache step)
• Add actions/setup-python@v5 pinned to Python 3.11
• Upgrade codecov/codecov-action v1 → v4
• Skip TestBindSimple and TestBindCgoPackage

Why Python 3.11? Pinning avoids Python 3.12 breakage while we focus on
infrastructure. The two skipped tests fail due to a known Go 1.21+ CGO
limitation when multiple C-shared libraries are loaded in the same process
(see #370).

Similar to #378 by @coffeemakingtoaster.

Co-authored-by: @coffeemakingtoaster mh340@hdm-stuttgart.de

[2/6] Enable CI for stacked PRs targeting any branch — b-long#4

Updates the pull_request trigger from branches: [master] to
branches: ['**'] so GitHub Actions CI runs on stacked PRs that target
feature branches rather than only master.

[3/6] Add Go 1.24.x to CI test matrix — b-long#5

Adds Go 1.24.x alongside existing 1.22.x and 1.21.x matrix entries.

Based on #378 by @coffeemakingtoaster.

Note: two tests remain skipped due to known Go 1.21+ CGO issues (expected).

Co-authored-by: Max mh340@hdm-stuttgart.de

[4/6] Add C23 compatibility for bool typedef — b-long#6

Wraps typedef uint8_t bool; with #ifndef __cplusplus / #if !defined(bool)
preprocessor guards to avoid conflicts with C23's native bool type. This
fixes compilation errors with newer C compilers that default to the C23
standard.

Based on #379 by @deuill.

Co-authored-by: Marid de Uill maridlcueto@gmail.com

[5/6] Add Go 1.25.x to CI test matrix and update dependencies — b-long#8

Adds Go 1.25.x alongside 1.24.x, 1.22.x, and 1.21.x. Upgrades
golang.org/x/tools from v0.16.0 → v0.29.0 and updates the go.mod go
directive to 1.22.0 (set by go mod tidy).

Why the dependency update? Go 1.25 introduced breaking changes that make
golang.org/x/tools v0.16.0 incompatible:

golang.org/x/tools@v0.16.0/internal/tokeninternal/tokeninternal.go:78:9:
invalid array length -delta * delta (constant -256 of type int64)

Upgrading to v0.29.0 resolves this.

[6/6] Resume Windows testing — b-long#10

Re-enables the Windows runner and addresses two issues that were blocking it:

1. LF line endings — adds .gitattributes enforcing eol=lf for text
   files. TestCheckSupportMatrix does a byte-level comparison of
   SUPPORT_MATRIX.md; on Windows, Git's CRLF conversion caused spurious
   failures even though the content was correct.

2. Test matrix — simplifies and expands the matrix configuration.

3. Docs — adds notes to CONTRIBUTING.md / test docs on installing
   psutil before running the test suite on Windows.

---

Attribution

Several changes in this PR are based on or inspired by prior community
contributions:

Upstream PR	Author	Topic
#378	@coffeemakingtoaster	Actions modernization & Go 1.24
#379	@deuill	C23 bool typedef fix