Meta: Add basic clang-tidy configuration

Add a basic clang-tidy configuration that enables checks from the
following categories:

- bugprone
- cert
- clang-analyzer
- concurrency
- misc
- performance
- portability
- readability

The noisiest rules that have conflicts with the project style guide or
accepted practices have been turned off.

There's absolutely more work to be done here before we could consider
setting any of these warnings as errors and enforcing them in CI, but
committing a project clang-tidy configuration should help the rules
become more visible and let other contributors take a crack at tweaking
rules and/or finding possible bugs.

Sadly the cpp-core-guidelines and modernize categories are very, very
noisy. If we want to enable rules from these categories, they would need
to be on a rule by rule basis.

.clang-tidy

@@ -0,0 +1,48 @@
+---
+# Globally Disabled checks:
+#
+# bugprone-easily-swappable-parameters: This warning is loud with no clear advice on how to fix the potential problem
+# FIXME: bugprone-macro-parentheses: Enable with clang-tidy-14 when NOLINTBEGIN/NOLINTEND are available for code generating macros
+# bugprone-reserved-identifier: LibC headers that show up in the header filter are part of "the implementation"
+#   cert-dcl37-c: Alias for bugprone-reserved-identifier
+#   cert-dcl51-cpp: Alias for bugprone-reserved-identifier
+# cert-dcl21-cpp: No reference to this rule exists on Carnegie Mellon's SEI CERT C++ Confluence. And the suggestion is unusual
+# FIXME: misc-non-private-member-variables-in-classes: Audit uses of protected member variables to see if they really need to be protected
+# performance-noexcept-move-constructor: The project does not use exceptions, so there are no such optimizations available
+# performance-no-int-to-ptr: This rule flags every pointer to integer cast, which gets quite noisy. Should only be enabled on a case-by-case basis
+# readability-braces-around-statements: Redundant braces around single-line conditions is against project style
+# readability-magic-numbers: This check is very noisy in the codebase, especially in AK.
+# readability-named-parameter: We frequently omit parameter names to work around -Wunused-parameter
+# FIXME: readability-uppercase-literal-suffix: Enable this check, the rationale is solid but the findings are numerous
+#
+Checks: >
+  -*,
+  bugprone-*,
+  cert-*,
+  clang-analyzer-*,
+  concurrency-*,
+  misc-*,
+  performance-*,
+  portability-*,
+  readability-*,
+  -bugprone-easily-swappable-parameters,
+  -bugprone-macro-parentheses,
+  -bugprone-reserved-identifier,-cert-dcl37-c,-cert-dcl51-cpp,
+  -cert-dcl21-cpp,
+  -misc-non-private-member-variables-in-classes,
+  -performance-noexcept-move-constructor,
+  -performance-no-int-to-ptr,
+  -readability-braces-around-statements,
+  -readability-magic-numbers,
+  -readability-named-parameter,
+  -readability-uppercase-literal-suffix,
+WarningsAsErrors: ''
+HeaderFilterRegex: 'AK|Userland|Kernel|Tests'
+FormatStyle: none
+CheckOptions:
+  - key: misc-non-private-member-variables-in-classes.IgnoreClassesWithAllMemberVariablesBeingPublic
+    value: true
+  - key: readability-implicit-bool-conversion.AllowPointerConditions
+    value: true
+  - key: readability-function-cognitive-complexity.Threshold
+    value: 100 # FIXME: Lower this (30? 50?), and refactor complex functions

AK/.clang-tidy

@@ -0,0 +1,7 @@
+---
+# Disabled checks:
+#
+# misc-unused-using-decls: AK exports all public names into the global namespace per project style
+#
+Checks: '-misc-unused-using-decls'
+InheritParentConfig: true