[Enhancement] Better Lspsaga subtypes and Lspsaga supertypes LSP filtering

[pidgeon777]

When running the following commands:

• Lspsaga subtypes
• Lspsaga supertypes

a pop-up appears asking to select the wished LSP to perform the TypeHierarchy request.

For example, in the case of Python** it is possible in my buffer to select between:

• basedpyright
• ruff
• copilot

copilot wouldn't make sense and it is suggested on every buffer where it is active.

To solve this, I would propose for example to check if the LSP attached to the buffer supports the TypeHierarchy capability, before showing it in the pop-up.

Also, maybe it would be technically possible to merge all of the results provided by the remaining LSPs?