Generate dependency versions header from CMake (#22561)

## Summary

This PR introduces a CMake-generated header file containing all
dependency versions, eliminating the need for C++ code to depend on
Zig-exported version constants.

## Changes

- **New CMake script**: `cmake/tools/GenerateDependencyVersions.cmake`
that:
  - Reads versions from the existing `generated_versions_list.zig` file
- Extracts semantic versions from header files where available
(libdeflate, zlib)
- Generates `bun_dependency_versions.h` with all dependency versions as
compile-time constants
  
- **Updated BunProcess.cpp**:
  - Now includes the CMake-generated `bun_dependency_versions.h`
  - Uses `BUN_VERSION_*` constants instead of `Bun__versions_*` 
  - Removes dependency on Zig-exported version constants

- **Build system updates**:
  - Added `GenerateDependencyVersions` to main CMakeLists.txt
  - Added build directory to include paths in BuildBun.cmake

## Benefits

✅ Single source of truth for dependency versions
✅ Versions accessible from C++ without Zig exports
✅ Automatic regeneration during CMake configuration
✅ Semantic versions shown where available (e.g., zlib 1.2.8 instead of
commit hash)
✅ Debug output file for verification

## Test Results

Verified that `process.versions` correctly shows all dependency
versions:

```javascript
$ bun -e "console.log(JSON.stringify(process.versions, null, 2))"
{
  "node": "24.3.0",
  "bun": "1.2.22-debug",
  "boringssl": "29a2cd359458c9384694b75456026e4b57e3e567",
  "libarchive": "898dc8319355b7e985f68a9819f182aaed61b53a",
  "mimalloc": "4c283af60cdae205df5a872530c77e2a6a307d43",
  "webkit": "0ddf6f47af0a9782a354f61e06d7f83d097d9f84",
  "zlib": "1.2.8",
  "libdeflate": "1.24",
  // ... all versions present and correct
}
```

## Generated Files

- `build/debug/bun_dependency_versions.h` - Header file with version
constants
- `build/debug/bun_dependency_versions_debug.txt` - Human-readable
version list

🤖 Generated with [Claude Code](https://claude.ai/code)

---------

Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

CMakeLists.txt

@@ -43,6 +43,9 @@ include(SetupEsbuild)
 include(SetupZig)
 include(SetupRust)
 
+# Generate dependency versions header
+include(GenerateDependencyVersions)
+
 # --- Targets ---
 
 include(BuildBun)