fix(lsp): make spec complient JSON-RPC response and properly implement definition link suport

[Kara-Zor-El]

Howdy,

I'm working on making a Neovim plugin for the LSP and I got some errors, when looking into them I discovered there was some issues with the LSP:

• definitionProvider must be a boolean (or DefinitionOptions) see here: https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#serverCapabilities
• linkSupport was moved into definition.clientCapabilities and typeDefinition.clientCapabilities
• locationLink was previously assumed always an option but some clients only support location
• json-rpc result sucess messages should've not included the null error field (technically doesn't explicitly say in the spec field but specified in json-rpc (https://www.jsonrpc.org/specification#response_object) and breaks neovim)
• json-rpc error messages should've not included the null result field (https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#responseMessage)

sorry for how link dense the links are 🥲

[spotandjake]

Looks great to me just two nits

[spotandjake]

This looks good to me.