Merge pull request swiftlang#72373 from apple/shahmishal/main-swift6-update-checkout

[main][update-checkout] Add Swift 6.0 branch support

Author: shahmishal

utils/update_checkout/update-checkout-config.json

@@ -152,6 +152,55 @@
                 "zlib": "v1.3"
             }
         },
+        "release/6.0": {
+            "aliases": ["swift/release/6.0", "release/6.0"],
+            "repos": {
+                "llvm-project": "swift/release/6.0",
+                "swift-llvm-bindings": "swift/release/6.0",
+                "swift": "release/6.0",
+                "cmark": "release/6.0",
+                "llbuild": "release/6.0",
+                "swift-tools-support-core": "release/6.0",
+                "swiftpm": "release/6.0",
+                "swift-argument-parser": "1.2.3",
+                "swift-atomics": "1.2.0",
+                "swift-collections": "1.0.5",
+                "swift-crypto": "3.0.0",
+                "swift-certificates": "1.0.1",
+                "swift-asn1": "1.0.0",
+                "swift-driver": "main",
+                "swift-numerics": "1.0.2",
+                "swift-syntax": "release/6.0",
+                "swift-system": "1.2.1",
+                "swift-stress-tester": "release/6.0",
+                "swift-corelibs-xctest": "release/6.0",
+                "swift-corelibs-foundation": "release/6.0",
+                "swift-corelibs-libdispatch": "release/6.0",
+                "swift-integration-tests": "release/6.0",
+                "swift-xcode-playground-support": "release/6.0",
+                "ninja": "release",
+                "yams": "5.0.1",
+                "cmake": "v3.24.2",
+                "indexstore-db": "release/6.0",
+                "sourcekit-lsp": "release/6.0",
+                "swift-format": "release/6.0",
+                "swift-installer-scripts": "release/6.0",
+                "swift-docc": "release/6.0",
+                "swift-lmdb": "release/6.0",
+                "swift-docc-render-artifact": "release/6.0",
+                "swift-docc-symbolkit": "release/6.0",
+                "swift-markdown": "release/6.0",
+                "swift-nio": "2.31.2",
+                "swift-nio-ssl": "2.15.0",
+                "swift-experimental-string-processing": "swift/release/6.0",
+                "wasi-libc": "wasi-sdk-20",
+                "wasmkit": "0.0.3",
+                "curl": "curl-8_4_0",
+                "icu": "maint/maint-69",
+                "libxml2": "v2.11.5",
+                "zlib": "v1.3"
+            }
+        },
         "release/5.10": {
             "aliases": ["swift/release/5.10", "release/5.10"],
             "repos": {