Refactor CPUVendor

[codefiles]

Addresses the following:

pyright

  archinstall/lib/hardware.py:25:11 - error: Type "Literal[CpuVendor._Unknown]" is not assignable to return type "Self@CpuVendor"
    Type "Literal[CpuVendor._Unknown]" is not assignable to type "Self@CpuVendor" (reportReturnType)

pyrefly

ERROR Returned type `Literal[CpuVendor._Unknown]` is not assignable to declared return type `Self@CpuVendor` [bad-return]
  --> archinstall/lib/hardware.py:25:11
   |
20 |     def get_vendor(cls, name: str) -> Self:
   |                                       ---- declared return type
21 |         if vendor := getattr(cls, name, None):
22 |             return vendor
23 |         else:
24 |             debug(f"Unknown CPU vendor '{name}' detected.")
25 |             return cls._Unknown
   |                    ^^^^^^^^^^^^
   |

ty

error[invalid-return-type]: Return type does not match returned value
  --> archinstall/lib/hardware.py:20:36
   |
20 |     def get_vendor(cls, name: str) -> Self:
   |                                       ---- Expected `Self@get_vendor` because of return type
21 |         if vendor := getattr(cls, name, None):
22 |             return vendor
23 |         else:
24 |             debug(f"Unknown CPU vendor '{name}' detected.")
25 |             return cls._Unknown
   |                    ^^^^^^^^^^^^ expected `Self@get_vendor`, found `Literal[CpuVendor._Unknown]`
   |