a more general version of https://github.com/rust-lang/rust/pull/146080.
after a bit of hacking in [`fluent.rs`](https://github.com/rust-lang/rust/blob/master/compiler/rustc_fluent_macro/src/fluent.rs), i discovered that i'm not the only one that is bad at following guidelines 😅. this pr lowercases the first letter of all the error messages in the codebase.
(i did not change things that are traditionally uppercased such as _MIR_, _ABI_ or _C_)
i think it's reasonable to run a `@bors try` so all the test suite is checked, as i cannot run some of the tests on my machine. i double checked (and replaced manually) all the old error messages, but better be safe than sorry.
in the future i will try to add a check in `x test tidy` that errors if an error message starts with an uppercase letter.
This makes it easier to open the messages file while developing on features.
The commit was the result of automatted changes:
for p in compiler/rustc_*; do mv $p/locales/en-US.ftl $p/messages.ftl; rmdir $p/locales; done
for p in compiler/rustc_*; do sed -i "s#\.\./locales/en-US.ftl#../messages.ftl#" $p/src/lib.rs; done
