`url.join(...)` drops parts of the path if `url` does not end with `/`

### Describe the bug

I'm joining two parts of an URL:
1. One URL with the host and first part of the path
2. One URL with the second part of the path and query params

Expected behaviour: The result path is concatenated from the two parts.
Actual behaviour: The result path is concatenated but drops the last part of the first URL if the first URL does not endwith a "/"

### To Reproduce

```python
import pytest
from yarl import URL

@pytest.mark.parametrize(
"first_url_part",
[
pytest.param(URL("https://example.inv/Foo/Bar"), id="w/o trailing slash"),
pytest.param(URL("https://example.inv/") / "Foo" / "Bar", id="dynamically without trailing slash"),
pytest.param(URL("https://example.inv/Foo/Bar/"), id="with trailing slash"),
pytest.param(URL("https://example.inv/") / "Foo" / "Bar/", id="dynamically with trailing slash"),
],
)
def test_url_join(first_url_part: URL):
assert isinstance(first_url_part, URL)
second_url_part = URL("Baz/asd?xyz=123")
actual = first_url_part.join(second_url_part)
assert actual == URL("https://example.inv/Foo/Bar/Baz/asd?xyz=123")
# for 'w/o trailing slash' case the assertion is not fulfilled
# Expected :URL('https://example.inv/Foo/Bar/Baz/asd?xyz=123')
# Actual :URL('https://example.inv/Foo/Baz/asd?xyz=123') # <-- why is the '/Bar/' part missing?
```

### Expected behavior

The last part of the first URL path should _not_ be dropped.

### Test Output

```python-traceback
========================= 3 failed, 1 passed in 0.13s =========================
FAILED [ 25%]
unittests\urltest.py:4 (test_url_join[w/o trailing slash])
URL('https://example.inv/Foo/Baz/asd?xyz=123') != URL('https://example.inv/Foo/Bar/Baz/asd?xyz=123')

Expected :URL('https://example.inv/Foo/Bar/Baz/asd?xyz=123')
Actual :URL('https://example.inv/Foo/Baz/asd?xyz=123')

first_url_part = URL('https://example.inv/Foo/Bar')

@pytest.mark.parametrize(
"first_url_part",
[
pytest.param(URL("https://example.inv/Foo/Bar"), id="w/o trailing slash"),
pytest.param(URL("https://example.inv/") / "Foo" / "Bar", id="dynamically without trailing slash"),
pytest.param(URL("https://example.inv/Foo/Bar/"), id="with trailing slash"),
pytest.param(URL("https://example.inv/") / "Foo" / "Bar/", id="dynamically with trailing slash"),
],
)
def test_url_join(first_url_part: URL):
assert isinstance(first_url_part, URL)
second_url_part = URL("Baz/asd?xyz=123")
actual = first_url_part.join(second_url_part)
> assert actual == URL("https://example.inv/Foo/Bar/Baz/asd?xyz=123")
E AssertionError: assert URL('https://example.inv/Foo/Baz/asd?xyz=123') == URL('https://example.inv/Foo/Bar/Baz/asd?xyz=123')
E + where URL('https://example.inv/Foo/Bar/Baz/asd?xyz=123') = URL('https://example.inv/Foo/Bar/Baz/asd?xyz=123')

urltest.py:18: AssertionError
FAILED [ 50%]
unittests\urltest.py:4 (test_url_join[dynamically without trailing slash])
URL('https://example.inv/Foo/Baz/asd?xyz=123') != URL('https://example.inv/Foo/Bar/Baz/asd?xyz=123')

Expected :URL('https://example.inv/Foo/Bar/Baz/asd?xyz=123')
Actual :URL('https://example.inv/Foo/Baz/asd?xyz=123')

first_url_part = URL('https://example.inv/Foo/Bar')

@pytest.mark.parametrize(
"first_url_part",
[
pytest.param(URL("https://example.inv/Foo/Bar"), id="w/o trailing slash"),
pytest.param(URL("https://example.inv/") / "Foo" / "Bar", id="dynamically without trailing slash"),
pytest.param(URL("https://example.inv/Foo/Bar/"), id="with trailing slash"),
pytest.param(URL("https://example.inv/") / "Foo" / "Bar/", id="dynamically with trailing slash"),
],
)
def test_url_join(first_url_part: URL):
assert isinstance(first_url_part, URL)
second_url_part = URL("Baz/asd?xyz=123")
actual = first_url_part.join(second_url_part)
> assert actual == URL("https://example.inv/Foo/Bar/Baz/asd?xyz=123")
E AssertionError: assert URL('https://example.inv/Foo/Baz/asd?xyz=123') == URL('https://example.inv/Foo/Bar/Baz/asd?xyz=123')
E + where URL('https://example.inv/Foo/Bar/Baz/asd?xyz=123') = URL('https://example.inv/Foo/Bar/Baz/asd?xyz=123')

urltest.py:18: AssertionError
PASSED [ 75%]FAILED [100%]
unittests\urltest.py:4 (test_url_join[dynamically with trailing slash])
URL('https://example.inv/Foo/Baz/asd?xyz=123') != URL('https://example.inv/Foo/Bar/Baz/asd?xyz=123')

Expected :URL('https://example.inv/Foo/Bar/Baz/asd?xyz=123')
Actual :URL('https://example.inv/Foo/Baz/asd?xyz=123')

first_url_part = URL('https://example.inv/Foo/Bar')

@pytest.mark.parametrize(
"first_url_part",
[
pytest.param(URL("https://example.inv/Foo/Bar"), id="w/o trailing slash"),
pytest.param(URL("https://example.inv/") / "Foo" / "Bar", id="dynamically without trailing slash"),
pytest.param(URL("https://example.inv/Foo/Bar/"), id="with trailing slash"),
pytest.param(URL("https://example.inv/") / "Foo" / "Bar/", id="dynamically with trailing slash"),
],
)
def test_url_join(first_url_part: URL):
assert isinstance(first_url_part, URL)
second_url_part = URL("Baz/asd?xyz=123")
actual = first_url_part.join(second_url_part)
> assert actual == URL("https://example.inv/Foo/Bar/Baz/asd?xyz=123")
E AssertionError: assert URL('https://example.inv/Foo/Baz/asd?xyz=123') == URL('https://example.inv/Foo/Bar/Baz/asd?xyz=123')
E + where URL('https://example.inv/Foo/Bar/Baz/asd?xyz=123') = URL('https://example.inv/Foo/Bar/Baz/asd?xyz=123')

urltest.py:18: AssertionError

Process finished with exit code 1
```

### Python Version

```console
3.11.0
```

### multidict Version

```console
multidict==6.0.4
```

### yarl Version

```console
yarl==1.9.2
```

### OS

Windows

### Additional context

_No response_

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