Add support for Enums to filename sniff

[jaymcp]

Description

Updates our file name sniff to account for enums correctly.
Enums should follow the same rules as interfaces, classes, and traits:

• one object per file
• file name should be lower-kebab case, and be prefixed with enum-

This PR also remove some template checks that came from the original Sniff, but are not required for our purposes.

Testing steps

composer require --dev bigbite/phpcs-config:dev-feat/enum-filenames

Create a file called enum-my-enum.php:

enum My_Enum {
    case Foo;
}

Run

./vendor/bin/phpcs .

There should be no errors.

Then try:

• renaming the file or renaming the enum
• adding a second enum to the same file

Run ./vendor/bin/phpcs . after every change.
If the filename isn't exactly the lower-kebab case name of the enum, prefixed with enum-, PHPCS should error.

Types of changes (if applicable):

• Bug fix (non-breaking change which fixes an issue).
• New feature (non-breaking change which adds functionality).
• Breaking change (fix or feature that would cause existing functionality to not work as expected).

Checklist (if applicable):

• All checks pass when running `composer run all-checks.

[ampersarnie]

Tested the following enum setups:

• Enums
• Back Enums.
• Enum Methods.
• Enum Methods with an Interface.
• Enum constants.