Support for LSP v3.16 (finalized specification)

[pappleby]

Description:
lsp4intellij currently supports the proposal version of the LSP v3.16 spec instead of the final released version.

Describe your problem(s)
LSP clients using the finalized v3.16 spec get their processes killed by the plugin if they use anything that changed between the final and proposed versions. Release notes for LSP4J has a list of these breaking changes.

Describe your solution(s)
Update the LSP4J dependency to it's latest release (v0.12.0 right now, v0.13.0 looks like it's in the works).