Improve CodeAction performance with CodeAction#data & resolveCodeAction

[angelozerr]

LSP 3.16 provides 2 new CodeAction support that LemMinx should use for their code action:

• resolveCodeAction -> https://github.com/eclipse/lsp4j/blob/c0b921895b4576feeb355eea7a053a0d56daba7b/org.eclipse.lsp4j/src/main/java/org/eclipse/lsp4j/services/TextDocumentService.java#L263

For instance, LemMinx provides several code action to generate XSD, DTD from the given XML file which is not bound to a grammar. This process should be done in the resolveCodeAction instead of doing that every time that XML root element is hovered.

• use CodeAction#data -> https://github.com/eclipse/lsp4j/blob/985a92bc0a0f543aa379edecbf0ddd56bed4df6f/org.eclipse.lsp4j/src/main/xtend-gen/org/eclipse/lsp4j/CodeAction.java#L104

For instance, when a XML doesn't respect a XSD, for an element, we have a CodeAction which suggest the proper element. This CodeAction recompute those available elements although the validation provided them. The idea is to generate diagnostics with data which contains allowed element (coming from the Xerces XSD validator) https://github.com/eclipse/lsp4j/blob/985a92bc0a0f543aa379edecbf0ddd56bed4df6f/org.eclipse.lsp4j/src/main/xtend-gen/org/eclipse/lsp4j/Diagnostic.java#L93 and code action will be able to reuse this data instead of recomputing allowed elements.