Warn on conflicting keys of src/cargo/util/toml/mod.rs #10317
Description
Problem
a few of fields in src/cargo/util/toml/mod.rs have alternative name. When they are set at the same time, we should
warn about conflicting keys.
Possible Solution(s)
Warn when two keys are set that control the same thing.
Notes
From: #10316 (comment)