impl Completions: Auto import submodules. #2207

[asukaminato0721]

Summary

part of #2207

Added auto-import suggestions for submodules so completions insert from <parent> import <submodule> (and corresponding quickfix entries).

Test Plan

Added a new LSP completion test and fixtures.

[Copilot]

Pull request overview

This PR implements auto-import suggestions for submodules as part of issue #2207. When a user types a submodule name that's not imported, the IDE will now suggest adding from <parent_module> import <submodule> imports, both in completions and as quick-fix code actions.

Changes:

• Added auto-import completion support for submodules that generates from parent import submodule style imports
• Added corresponding code action (quick-fix) suggestions for importing submodules
• Added comprehensive test coverage with new test fixtures and test case

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
pyrefly/lib/test/lsp/lsp_interaction/test_files/autoimport_submodule/pyrefly.toml	Test configuration file defining search path
pyrefly/lib/test/lsp/lsp_interaction/test_files/autoimport_submodule/foo.py	Test file with copyright header (content added dynamically in test)
pyrefly/lib/test/lsp/lsp_interaction/test_files/autoimport_submodule/autoimport_submodule_pkg/auto_submodule.py	Test submodule containing a VALUE constant for testing
pyrefly/lib/test/lsp/lsp_interaction/test_files/autoimport_submodule/autoimport_submodule_pkg/init.py	Package initialization file for test package
pyrefly/lib/test/lsp/lsp_interaction/completion.rs	New test case validating submodule auto-import completions
pyrefly/lib/state/lsp.rs	Added code action logic to suggest submodule imports in quick-fix suggestions
pyrefly/lib/lsp/wasm/completion.rs	Added completion item logic to suggest submodule imports in auto-completion

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[github-actions]

According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅