New feature: call hierarchy support

[jneira]

• It is a feature common in other ides like eclipse or intellij
• It shows the graph of all transitive calls of a function, in a tree:
  • The nodes are selectable (shows info in the right pane) and navigable with ctrl+click
  • In the right pane other info like the possible multiple calls in the same funcion, with the line number (also navigables to the concrete line)

• It could use @wz1000 HieDB, like the recent find references implementation
• It is supported in lsp 3.16:
  • https://microsoft.github.io/language-server-protocol/specifications/specification-3-16/
  • microsoft/language-server-protocol#468

[jneira]

This would need add support for that feature in haskell-lsp:

• lsp spec: https://microsoft.github.io/language-server-protocol/specifications/specification-3-16/
• lsp-haskell issue: haskell/lsp#134