Implement SymbolInformation.overrides

[olafurpg]

Currently, "find references" only returns results for the exact symbol over the cursor. The results don't include methods that override that symbol, or the supermethod of a symbol.

• implement the new SymbolInformation.overrides feature that got added to SemanticDB Add information about overrides to symbol information scalameta/scalameta#2233
• extend lsif-semanticdb conversion to include overrides in the "find references" results

[Strum355]

Related to https://github.com/sourcegraph/sourcegraph/issues/15699.

First look indicates JavacTypes.getOverridenMethods may be a viable route. Will investigate

[Strum355]

Testing seems to confirm the previous comment