pkg: replace @cImport with addTranslateC in pkg/

@cImport is going to disappear in Zig 0.17. Its deprecated in Zig 0.16.
Let's remove it now.

Replace @cImport with addTranslateC across pkg/ packages. Each
package now has a c_import.h header that is translated at build
time via addTranslateC and exposed as a "cimport" module import.

Converted packages:
- dcimgui
- fontconfig
- freetype
- glslang
- harfbuzz
- macos
- oniguruma
- opengl
- sentry
- spirv-cross
- wuffs

Omitted:
- gtk4-layer-shell - This has a bit more complexity with how it
  interacts with GTK headers, so I need to consider this a bit more.
- src/ - It'll be cleaner to do this separately.

pkg/macos/graphics/bitmap_context.zig

@@ -3,7 +3,7 @@ const assert = std.debug.assert;
 const Allocator = std.mem.Allocator;
 const graphics = @import("../graphics.zig");
 const Context = @import("context.zig").Context;
-const c = @import("c.zig").c;
+const c = @import("c");
 
 pub const BitmapContext = opaque {
     pub const context = Context(BitmapContext);