Make enum values final

[joey-laminar]

#10852 made it so that boolean values are correctly identified as Literals in an enum. Other values seem to not be:

from enum import Enum

class Truth(Enum):
    true = True
    false = False

class MyInt(Enum):
    a = 0
    b = 1

class MyStr(Enum):
    a = "a"
    b = "b"

reveal_type(Truth.false.value)
reveal_type(MyInt.a.value)
reveal_type(MyStr.a.value)

Results in:

a.py:15: note: Revealed type is "Literal[False]?"
a.py:16: note: Revealed type is "builtins.int"
a.py:17: note: Revealed type is "builtins.str"

Expected result:

a.py:15: note: Revealed type is "Literal[False]?"
a.py:16: note: Revealed type is "Literal[0]"
a.py:17: note: Revealed type is "Literal['a']"

The enum members themselves (MyInt.a) are correctly identified as final, but their values should be as well

[joey-laminar]

Some experimentation shows that commenting out lvalue.is_inferred_def = False inside of store_declared_types in semanal.py fixes this issue, although I'm sure it breaks a bunch of other things. I don't yet understand enough to know why this is called for all types except bool