Fix name conflicts caused by the `SystemParam` and `WorldQuery` macros

[joseph-gio]

Objective

Fix #1727 Fix #8010

Meta types generated by the SystemParam and WorldQuery derive macros can conflict with user-defined types if they happen to have the same name.

Solution

In order to check if an identifier would conflict with user-defined types, we can just search the original TokenStream passed to the macro to see if it contains the identifier (since the meta types are defined in an anonymous scope, it's only possible for them to conflict with the struct definition itself). When generating an identifier for meta types, we can simply check if it would conflict, and then add additional characters to the name until it no longer conflicts with anything.

The WorldQuery "Item" and read-only structs are a part of a type's public API, and thus it is intended for them to conflict with user-defined types.