CI: fix outdated Node.js warnings, clean up Windows and Go setup

[Lekensteyn]

• ci: use latest GitHub Actions versions to fix Node.js 20 warnings

• ci: use newer clang version on Windows, fix Test job name

  • bindgen relies on clang-sys for parsing headers. Replace the old LLVM
    version in favor of LLVM 20 from windows-latest (windows-2025)..
  • Drop explicit installation of nasm, the build log suggests that Perl's
    C:/Strawberry/c/bin/nasm.exe version is being used anyway.
  • Add missing x86_64-msvc-static thing to ensure that the job shows as
    Test (x86_64-msvc-static) instead of its properties,
    Test (x86_64-msvc-static, x86_64-pc-windows-msvc, ...)

• ci: update to Go 1.27, skip Go installation unless needed

  • Require Go 1.27 to match BoringSSL. Go is only needed to run BoringSSL
    tests or build with FIPS, remove it from other jobs.
  • Disable caching to silence a warning about missing go.sum.
  • Use latest setup-go action to upgrade from Node.js 20 to 24.

[Lekensteyn]

Some unrelated CI failures with a similar root cause as #520 - too many unrelated symbols.

I am going to investigate using allowlist_file to fix this for good.

For reference, relevant build logs:

error: suspicious definition of the runtime `malloc` symbol used by the standard library
     --> /home/runner/work/boring/boring/target/debug/build/boring-sys-b6bcf3ced43db56c/out/bindings.rs:11328:5
      |
11328 |     pub fn malloc(__size: ::std::os::raw::c_ulong) -> *mut ::std::os::raw::c_void;
      |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
      |
      = note: expected `unsafe extern "C" fn(usize) -> *mut c_void` (for the current target)
              found    `unsafe extern "C" fn(u64) -> *mut c_void`
      = help: either fix the signature or remove any attributes like `#[unsafe(no_mangle)]`, `#[unsafe(export_name = "malloc")]`, or `#[link_name = "malloc"]`
      = help: allow this lint if the signature is compatible
      = note: `-D suspicious-runtime-symbol-definitions` implied by `-D warnings`
      = help: to override `-D warnings` add `#[allow(suspicious_runtime_symbol_definitions)]`

error: suspicious definition of the runtime `realloc` symbol used by the standard library
     --> /home/runner/work/boring/boring/target/debug/build/boring-sys-b6bcf3ced43db56c/out/bindings.rs:11333:5
      |
11333 | /     pub fn realloc(
11334 | |         __ptr: *mut ::std::os::raw::c_void,
11335 | |         __size: ::std::os::raw::c_ulong,
11336 | |     ) -> *mut ::std::os::raw::c_void;
      | |_____________________________________^
      |
      = note: expected `unsafe extern "C" fn(*mut c_void, usize) -> *mut c_void` (for the current target)
              found    `unsafe extern "C" fn(*mut c_void, u64) -> *mut c_void`
      = help: either fix the signature or remove any attributes like `#[unsafe(no_mangle)]`, `#[unsafe(export_name = "realloc")]`, or `#[link_name = "realloc"]`
      = help: allow this lint if the signature is compatible