mypy plugin allows false positive error when exhaustively pattern matching on Result

# Bug report

## What's wrong

> Again, this is a **really** cool project ❤️

Consider the following code:

```py
from enum import Enum, auto
import math
from typing import TypeAlias

from returns.result import Failure, Result, Success

class MathError(Enum):
DivisionByZero = auto()
NonPositiveLogarithm = auto()

MathResult: TypeAlias = Result[float, MathError]

def div(x: float, y: float) -> MathResult:
if y == 0.0:
return Failure(MathError.DivisionByZero)

return Success(x / y)

def ln(x: float) -> MathResult:
if x <= 0.0:
return Failure(MathError.NonPositiveLogarithm)

return Success(math.log(x))

def op_(x: float, y: float) -> MathResult:
z = div(x, y)
match z:
case Success(ratio):
return ln(ratio)
case Failure(_):
return z
```

`mypy` configuration in `pyproject.toml`

```toml
[tool.mypy]
ignore_missing_imports = true
strict = true
plugins = [
"returns.contrib.mypy.returns_plugin",
]
```

Running:

```
$ mypy pattern_div.py
pattern_div.py:32: error: Missing return statement
```

Related to #1090

## How is that should be

As far as I can tell (new to `returns`), I'm matching exhaustively here, so I would not expect a `mypy` error.

`mypy` seems to understand exhaustive matching in general. `mypy` does not throw a type checking error in the following snippet.

```py
def test(err: MathError) -> int:
match err:
case MathError.DivisionByZero:
return 0
case MathError.NonPositiveLogarithm:
return 1
```

## System information

- `python` version: 3.10.2
- `returns` version: 0.19.0
- `mypy` version: 0.942

```
$ pip list
Package Version
----------------- -------
black 22.3.0
click 8.1.2
distlib 0.3.4
filelock 3.6.0
isort 5.10.1
mypy 0.942
mypy-extensions 0.4.3
packaging 21.3
pathspec 0.9.0
pep517 0.12.0
pip 22.0.4
pip-tools 6.6.0
platformdirs 2.5.1
pluggy 1.0.0
py 1.11.0
pyparsing 3.0.8
returns 0.19.0
setuptools 62.1.0
six 1.16.0
toml 0.10.2
tomli 2.0.1
tox 3.25.0
typing_extensions 4.1.1
virtualenv 20.14.1
wheel 0.37.1
```