Export works without import

[Akirathan]

Closes #9562

Pull Request Description

This PR enables exporting a symbol by FQN without the need to import it first. As a consequence, the following do-repeat-yourself pattern will no longer be needed in standard libraries main modules:

import project.Data.Vector.Vector
export project.Data.Vector.Vector

but can be replaced with simple:

export project.Data.Vector.Vector

Important Notes

ImportResolver traverses also the export statements, and checks if there is a corresponding import statement for it. If not, it tries to insert a synthetic import statement and resolve it.

Checklist

Please ensure that the following checklist has been satisfied before submitting the PR:

• The documentation has been updated, if necessary.
• Screenshots/screencasts have been attached, if there are any visual changes. For interactive or animated visual changes, a screencast is preferred.
• All code follows the
  Scala,
  Java,
  and
  Rust
  style guides. In case you are using a language not listed above, follow the Rust style guide.
• All code has been tested:
  • Unit tests have been written where possible.
  • If GUI codebase was changed, the GUI was tested when built using ./run ide build.

[Akirathan]

Changes in this PR are mentioned just in this paragraph. The rest of the diff to this documentation file is just an attempt to update the specification to correspond to the current functionality.

[JaroslavTulach]

This is a very nice change!