Set completion item's text edit if optional replacement span and insert text are present

[gabritto]

Fixes #1568.

As per my comment on the issue, the problem happens because in LSP, if an editRange is present in the completion response (i.e. we set a default editRange to be used for all completion items), then an item's insertText is ignored. This is in line with the behavior when you specify textEdits in individual items: insertText is also ignored in that case.
Ignoring insertText meant the client would use the item's label, e.g. name?, instead of the insertText's name.

We may get rid of this problem in the future if instead of appending ? in the item's label directly, we use the item's labelDetails.
But I want to fix the bug right away, and (1) not all clients support labelDetails, and (2) I'd like to have snippet completions implemented before figuring out the right labelDetails behavior, because snippet completions also use labelDetails.

[Copilot]

Pull Request Overview

This PR fixes a bug where completion items with insertText were not being properly applied when an editRange was set in the completion defaults. The issue occurred because LSP clients ignore insertText when editRange is present, causing items like optional properties to show their label (e.g., name?) instead of the intended insert text (e.g., name).

• Modifies completion logic to convert insertText to textEdit when editRange is set
• Updates affected test cases to expect textEdit instead of insertText
• Removes one test case that's no longer relevant

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
internal/ls/completions.go	Adds logic to convert insertText to textEdit when editRange is present in item defaults
internal/ls/completions_test.go	Removes test case for static class member completions
internal/fourslash/tests/manual/completionsWithDeprecatedTag4_test.go	Updates test to expect textEdit instead of insertText for optional property completion
internal/fourslash/tests/manual/completionsSelfDeclaring1_test.go	Updates test to expect textEdit instead of insertText for optional property completion
internal/fourslash/tests/manual/completionsAtIncompleteObjectLiteralProperty_test.go	Updates test to expect textEdit instead of insertText for optional property completion
internal/fourslash/tests/completionFilterText1_test.go	Updates multiple test cases to expect textEdit instead of insertText for private field completions
internal/fourslash/_scripts/manualTests.txt	Adds three test files to manual test list

[gabritto]

This test file will be deleted as part of the snapshopt PR, and we also have fourslash tests now, so I just deleted this test case instead of updating it.