Please document how conflicting configuration options resolve in cabal.project

In [the docs](https://cabal.readthedocs.io/en/stable/cabal-project.html#package-configuration-options) we have:

> - They can be specified at the top-level, in which case they apply only to local package, or
> - They can be specified inside a package stanza, in which case they apply to the build of the package, whether or not it is local or external.
> - They can be specified inside an package * stanza, in which case they apply to all packages, local ones from the project and also external dependencies.

but I don't see mention of how conflicts are resolved, e.g.

```
package foo
coverage: true

coverage: false
```

or...

```
coverage: false

package foo
coverage: true
```

...as well as how `import` comes into play (presumably treated like the files are concatenated). With the introduction of `import` knowing how to override particular earlier options becomes important and an obvious use-case.

Documentation will help users as well as help avoid what would be a disaster if cabal changed behavior.

Start with the cabal.project documentation section on package configuration options and compare its stated scopes with the conflicting `coverage` examples in the issue. Check the documented behavior of `import` and determine how later or more specific settings resolve conflicts. Done means the documentation clearly explains precedence, ordering, and import interactions.

Written by the indexing model from the issue text.