[clang-tidy] Add a new check in cppcoreguidelines for checking enum values' names

ISO C++ Core Guidelines section [Enum.5](https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#enum5-dont-use-all_caps-for-enumerators) states that ALL_CAPS should be avoided for enum names. The reason for this mentioned there is to avoid clashes with macros.

Example given there:

```c++
// webcolors.h (third party header)
#define RED 0xFF0000
#define GREEN 0x00FF00
#define BLUE 0x0000FF

// productinfo.h
// The following define product subtypes based on color

enum class Product_info { RED, PURPLE, BLUE }; // syntax error
```

Check can be something like - iterate through each possible enum value, check if it matches the regex `[A-Z0-9_]` and if it does, flag it.

Possible fix suggestion:

```c++
enum class Product_info { Red, Purple, Blue };
```

Start in clang-tidy's cppcoreguidelines checks and compare how existing checks are implemented and tested. Define the naming pattern precisely from the issue's Enum.5 example, then add coverage for uppercase and suggested mixed-case enumerators; done means the new check reliably reports the former without flagging the latter.

Written by the indexing model from the issue text.