Support linked correction proposals

[hopehadfield]

Add support for linked correction proposals, as is done in Eclipse

Currently, the same quickfix in vscode-java only gives the first option from the list.

[rgrunber]

The LSP Spec now supports SnippetTextEdit, so this is possible for code actions. You may have some difficulty sending it on the language server side with the existing lsp4j library as it lacks the necessary classes, but should be possible to work around that. The language client we use (vscode-languageserver-node) also seems to now support it.

[fbricon]

As usual, make sure the client supports it before sending SnippetTextEdits

[rgrunber]

An update from @hopehadfield :

[rgrunber]

We may have to live with the side effects of microsoft/vscode#63129 since the server-side snippets get an additional indentation.