This PR will fix some typos detected by [typos].
There are also some other typos in the function names, variable names, and file
names, which I leave as they are. I'm more certain that typos in comments
should be fixed.
[typos]: https://github.com/crate-ci/typos
When extracting a field expression, if RA was unable to resolve the type of the
field, we would previously fall back to using "var_name" as the variable name.
Now, when the `Expr` being extracted matches a `FieldExpr`, we can use the
`NameRef`'s ident token as a fallback option.
fixes#10035
