upgrade to Xcode 15.4 and Swift 5.10 on CI (#1472)

WIP, to unblock CI on open PRs

Author: aaronsky

.bazelci/presubmit.yml

@@ -4,7 +4,7 @@ x_defaults:
   # it doesn't know about; so that is used to avoid repeating common subparts.
   mac_common: &mac_common
     platform: macos_arm64
-    xcode_version: "15.2"
+    xcode_version: "15.4"
     build_targets:
       - "//examples/..."
     test_targets:
@@ -14,7 +14,7 @@ x_defaults:
     platform: ubuntu2004
     environment:
       CC: clang
-      SWIFT_VERSION: "5.9.2"
+      SWIFT_VERSION: "5.10.1"
       SWIFT_HOME: "$HOME/swift-$SWIFT_VERSION"
       PATH: "$SWIFT_HOME/usr/bin:$PATH"
   linux_common: &linux_common

.bcr/presubmit.yml

@@ -19,7 +19,7 @@ tasks:
     platform: ${{ platform }}
     environment:
       CC: "clang"
-      SWIFT_VERSION: "5.9.2"
+      SWIFT_VERSION: "5.10.1"
       SWIFT_HOME: "$HOME/swift-$SWIFT_VERSION"
       PATH: "$PATH:$SWIFT_HOME/usr/bin"
     shell_commands: *shell_commands