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/dispatch.zig

@@ -1,4 +1,4 @@
-pub const c = @import("dispatch/c.zig").c;
+pub const c = @import("c");
 pub const data = @import("dispatch/data.zig");
 pub const queue = @import("dispatch/queue.zig");
 pub const Data = data.Data;