Update to Zig 0.16.0

This commit represents the majority of the work necessary to upgrade
Ghostty to use Zig 0.16.0.

Key parts:

* In addition to its previous responsibilities, the global state now
  houses state for global I/O implementations and the process
  environment. It is now also utilized in the main application along
  with the C library. Where necessary, global state is isolated from key
  parts of the implementation (e.g., in libghostty subsystems), and it's
  expected that this list will grow.

* We currently manage our own C translation layer where necessary. In
  these cases, cImport has been removed in favor of the new external
  translate-c package. Due to fixes that have needed be made to properly
  translate the dependencies that were swapped out, as mentioned, we
  have had to backport fixes from the current translate-c package (and
  the upstream Arocc dependency). We will host this ourselves until Zig
  0.17.0 is released with these fixes.

* Where necessary (only a small number of cases), some stdlib code from
  0.15.2 (and even from 0.17.0) has been taken, adopted, and vendored in
  lib/compat.

Co-authored-by: Leah Amelia Chen <hi@pluie.me>

src/terminal/StringMap.zig

@@ -117,6 +117,7 @@ test "StringMap searchIterator" {
 
     const testing = std.testing;
     const alloc = testing.allocator;
+    const io = testing.io;
 
     // Initialize our regex
     try oni.testing.ensureInit();
@@ -130,7 +131,7 @@ test "StringMap searchIterator" {
     defer re.deinit();
 
     // Initialize our screen
-    var s = try Screen.init(alloc, .{ .cols = 5, .rows = 5, .max_scrollback = 0 });
+    var s = try Screen.init(io, alloc, .{ .cols = 5, .rows = 5, .max_scrollback = 0 });
     defer s.deinit();
     const str = "1ABCD2EFGH\n3IJKL";
     try s.testWriteString(str);
@@ -174,6 +175,7 @@ test "StringMap searchIterator URL detection" {
 
     const testing = std.testing;
     const alloc = testing.allocator;
+    const io = testing.io;
     const url = @import("../config/url.zig");
 
     // Initialize URL regex
@@ -188,7 +190,7 @@ test "StringMap searchIterator URL detection" {
     defer re.deinit();
 
     // Initialize our screen with text containing a URL
-    var s = try Screen.init(alloc, .{ .cols = 40, .rows = 5, .max_scrollback = 0 });
+    var s = try Screen.init(io, alloc, .{ .cols = 40, .rows = 5, .max_scrollback = 0 });
     defer s.deinit();
     try s.testWriteString("hello https://example.com/path world");
 
@@ -235,6 +237,7 @@ test "StringMap searchIterator URL with click position" {
 
     const testing = std.testing;
     const alloc = testing.allocator;
+    const io = testing.io;
     const url = @import("../config/url.zig");
 
     // Initialize URL regex
@@ -249,7 +252,7 @@ test "StringMap searchIterator URL with click position" {
     defer re.deinit();
 
     // Initialize our screen with text containing a URL
-    var s = try Screen.init(alloc, .{ .cols = 40, .rows = 5, .max_scrollback = 0 });
+    var s = try Screen.init(io, alloc, .{ .cols = 40, .rows = 5, .max_scrollback = 0 });
     defer s.deinit();
     try s.testWriteString("hello https://example.com world");