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)

For example the LSP spec deprecated symbolInformation so it is marked as deprecated in LSP code. I assume cases like this should not be removed from LSP4J as we should keep in LSP4J the same as the spec.

This means not removing deprecated fields and classes in the xtend files and the various service classes (like LanguageServer)

• 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)