Implement more handlers

[renkun-ken]

This PR implements the following handlers:

• prepareTypeHierarchy
• typeHierarchySupertypes
• typeHierarchySubtypes
• semanticTokens

and makes the following improvements:

• activeParameters in completion is supported.

• hierarchicalDocumentSymbolSupport is implemented so that class members are displayed in outline.

• The range of top-level symbols are fixed so that symbols defined in global scopes (enclosed in {} with or without if while etc) have correct ranges.

P.S: The code written in this PR is mostly done by @copilot.