Formatter: Parenthesize long expressions in dicts

[zanieb]

See #8436 for background.

Stable formatting of dicts with a long value results in a wrap that reduces readability

Unformatted:

if True:
    ___ = {
        "x": "---",
        "y": "--------------------------------------------------------------" if True else None,
        "z": "---",
    }

Formatted (Ruff, Black stable):

if True:
    ___ = {
        "x": "---",
        "y": "--------------------------------------------------------------"
        if True
        else None,
        "z": "---",
    }

Formatted (Black preview):

if True:
    ___ = {
        "x": "---",
        "y": (
            "--------------------------------------------------------------"
            if True
            else None
        ),
        "z": "---",
    }

With a shorter line, Ruff retains parenthesis when the lines are collapsed:

if True:
    ___ = {
        "x": "---",
        "y": ("----------------------------------------------------" if True else None),
        "z": "---",
    }

However, these parenthesis should be removed as they are superfluous.

Black's preview style will remove these parenthesis:

if True:
    ___ = {
        "x": "---",
        "y": "----------------------------------------------------" if True else None,
        "z": "---",
    }

See psf/black#620 psf/black#3440

Note that Black does not remove these parenthesis for calls or lists, see #8436 and #8438

[MichaReiser]

I merged this into #8438 and create a new issue for parenthesizing long values.