Meta: Switch to clang-format-16 as the standard formatter

This includes a few new options to the .clang-format configuration file
to A) adhere to option changes within clang-format 16 (namely the option
AlignTrailingComments), and B) enforce existing style guide rules with
new clang-format rules.

.devcontainer/devcontainer.json

@@ -7,7 +7,7 @@
         "ghcr.io/devcontainers/features/github-cli:1": {},
         "ghcr.io/devcontainers-contrib/features/pre-commit:1": {},
         "./features/serenity": {
-            "llvm_version": 15,
+            "llvm_version": 16,
             "enable_ladybird": true,
             "enable_serenity": true
         },

.devcontainer/features/serenity/devcontainer-feature.json

@@ -7,11 +7,11 @@
         "llvm_version": {
             "type": "string",
             "proposals": [
-                14,
                 15,
+                16,
                 "trunk"
             ],
-            "default": 15,
+            "default": 16,
             "description": "Select LLVM compiler version to use"
         },
         "enable_ladybird": {

.devcontainer/features/serenity/install.sh

@@ -3,7 +3,7 @@ set -e
 
 # Feature options
 
-LLVM_VERSION=${LLVM_VERSION:-15}
+LLVM_VERSION=${LLVM_VERSION:-16}
 ENABLE_LADYBIRD=${ENABLE_LADYBIRD:-true}
 ENABLE_SERENITY=${ENABLE_SERENITY:-true}