Generalize EntrypointProvider to MemberUsageProvider to allow constants & AST-based decision

[janedbal]

Renames (BC break):

# classes & methods
- `ShipMonk\PHPStan\DeadCode\Provider\MethodEntrypointProvider::getEntrypoints(): list<ReflectionMethod>` 
+ `ShipMonk\PHPStan\DeadCode\Provider\MemberUsageProvider::getUsages(): list<ClassMemberUsage>`

- `ShipMonk\PHPStan\DeadCode\Provider\SimpleMethodEntrypointProvider::isEntrypointMethod(): bool`
+ `ShipMonk\PHPStan\DeadCode\Provider\ReflectionBasedMemberUsageProvider::shouldMarkMethodAsUsed(): bool`

# neon config param
- `parameters.shipmonkDeadCode.entrypoints` 
+ `parameters.shipmonkDeadCode.usageProviders`

# neon service tag 
- `shipmonk.deadCode.entrypointProvider`
+ `shipmonk.deadCode.memberUsageProvider`