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/fontconfig/char_set.zig

@@ -1,6 +1,6 @@
 const std = @import("std");
 const assert = std.debug.assert;
-const c = @import("c.zig").c;
+const c = @import("c");
 
 pub const CharSet = opaque {
     pub fn create() *CharSet {