[bean completion proposals] avoid duplicate proposals

[martinlippert]

In #1518, I am seeing some duplicates in the list of bean proposals. This might happen when there are multiple bean definitions with the same name (maybe with different profiles). But showing all those duplicates doesn't make a lot of sense here, so we need to:

• probably include the bean type in the proposals (so that users can distinguish different proposals with the same bean name, but a different bean type)
• remove duplicates where the bean name and the bean type is the exact same, so applying those would result in the exact same code

[BoykoAlex]

Duplicates handling: 3a6dd8b and inclusion of type into the proposals just requires showing it visually in LSP4E: eclipse-lsp4e/lsp4e#1238

[BoykoAlex]

All LSP4E PRs have been merged. Marking as fixed.