Code Actions are not sorted by relevance

[Eskibear]

Currently, different kinds of proposals are sorted by ChangeCorrectionProposalComparator all together before converted to code actions. For proposals of different CodeActionKind, they are not sorted by relevance at all.

See https://github.com/eclipse/eclipse.jdt.ls/blob/1dfdeeafb9d0dd7c16d915763a30088dfa3a721e/org.eclipse.jdt.ls.core/src/org/eclipse/jdt/ls/core/internal/handlers/CodeActionHandler.java#L204-L223

Do we need to sort by relevance first?

[Eskibear]

If the actions should be grouped by CodeActionKind, 'quickfix' should be on top of the list if there's a problem. The current comparator compare CodeActionKind first, in alphabetical order. The order happened to be "quickfix", "refactor", "source". But now we have new kind "quickassist", which would be ahead of "quickfix" in alphabetical order.

So I'd like to use a more robust way:

• First sort actions by relevance for each CodeActionKind.
• Then combine the actions of different kinds.