[ty] Improve call inference for keyword-only `dict()` (#24103)
## Summary
We now infer keyword-only `dict(...)` calls like dict literals so that
bidirectional context applies to the values and the keyword names become
string-literal keys.
This is motivated by changes that came up in fixing ecosystem fallout
from https://github.com/astral-sh/ruff/pull/23946.
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Co-authored-by: David Peter <mail@david-peter.de>
