CI: update macOS runner to 13

Apple has already dropped support for macOS 12.
GitHub Actions is dropping macOS 12 support now.
The Zig project is also dropping macOS 12 support now.

This commit also bumps default minimum macos version to 13.

.github/workflows/ci.yaml

@@ -46,7 +46,7 @@ jobs:
       - name: Build and Test
         run: sh ci/aarch64-linux-release.sh
   x86_64-macos-release:
-    runs-on: "macos-12"
+    runs-on: "macos-13"
     env:
       ARCH: "x86_64"
     steps:

lib/std/Target.zig

@@ -531,7 +531,7 @@ pub const Os = struct {
                 },
                 .macos => .{
                     .semver = .{
-                        .min = .{ .major = 11, .minor = 7, .patch = 1 },
+                        .min = .{ .major = 13, .minor = 0, .patch = 0 },
                         .max = .{ .major = 15, .minor = 2, .patch = 0 },
                     },
                 },