Remove deprecated API

[jonahgraham]

There are a few categories of deprecated API in LSP4J. Most of the @Deprecated annotations are applied to constructs that are deprecated in the LSP and DAP specifications.

Use git grep -p -n -A1 @Deprecated for a quick view of all the deprecated Java with some context.

• Deprecated items still in LSP/DAP specs (not to be removed) but the @Deprecated annotations to be removed Please don't use Deprecated annotations for language server protocol deprecations #895

See #895, but having @Deprecated on LSP/DAP spec deprecations is not really helpful.

• Remove deprecated convenience constructors in xtend protocol files #875

There are numerous constructors in protocol files that are deprecated, such as one of the constructors of WorkspaceEditCapabilities

• Remove deprecated get/set properties in FormattingOptions #880

FormattingOptions getProperties and setProperties were deprecated in #99

• Remove deprecated LanguageServerAPI annotation #876

Long deprecated and replaced with the more generic JsonRpcData

• Remove deprecated methods Either class #877

Items such as all the helper methods in Either seem to be easy decisions to remove

• Remove deprecated factories #878

The various factories (like CollectionTypeAdapterFactory) seem to be easy decisions to remove

• Remove deprecated ResponseErrorCode.serverNotInitialized #879

This was a misspelling and is easy to remove

• Remove deprecated Websocket (javax version) javax.websocket #647

This was deprecated already in #647 (comment)

• Remove deprecated ConcurrentMessageProcessor.startProcessing #922

One extra item that was deprecated, but not included in the above items