feat(lsp): use stricter types for methods

This change modifies gen_lsp.lua so alias types are generated for
various types of lsp methods to distinguish between notifications
and requests:
 - vim.lsp.protocol.Method.ServerToClient.Request
 - vim.lsp.protocol.Method.ServerToClient.Notification
 - vim.lsp.protocol.Method.ClientToServer.Request
 - vim.lsp.protocol.Method.ClientToServer.Notification

 These types are then used instead of `string` where appropriate.

runtime/lua/vim/lsp/protocol.lua

@@ -621,22 +621,15 @@ function protocol.resolve_capabilities(server_capabilities)
 end
 
 -- Generated by gen_lsp.lua, keep at end of file.
---- @alias vim.lsp.protocol.Method.ClientToServer
+--- @alias vim.lsp.protocol.Method.ClientToServer.Request
 --- | 'callHierarchy/incomingCalls',
 --- | 'callHierarchy/outgoingCalls',
 --- | 'codeAction/resolve',
 --- | 'codeLens/resolve',
 --- | 'completionItem/resolve',
 --- | 'documentLink/resolve',
---- | '$/setTrace',
---- | 'exit',
 --- | 'initialize',
---- | 'initialized',
 --- | 'inlayHint/resolve',
---- | 'notebookDocument/didChange',
---- | 'notebookDocument/didClose',
---- | 'notebookDocument/didOpen',
---- | 'notebookDocument/didSave',
 --- | 'shutdown',
 --- | 'textDocument/codeAction',
 --- | 'textDocument/codeLens',
@@ -645,10 +638,6 @@ end
 --- | 'textDocument/declaration',
 --- | 'textDocument/definition',
 --- | 'textDocument/diagnostic',
---- | 'textDocument/didChange',
---- | 'textDocument/didClose',
---- | 'textDocument/didOpen',
---- | 'textDocument/didSave',
 --- | 'textDocument/documentColor',
 --- | 'textDocument/documentHighlight',
 --- | 'textDocument/documentLink',
@@ -676,19 +665,11 @@ end
 --- | 'textDocument/semanticTokens/range',
 --- | 'textDocument/signatureHelp',
 --- | 'textDocument/typeDefinition',
---- | 'textDocument/willSave',
 --- | 'textDocument/willSaveWaitUntil',
 --- | 'typeHierarchy/subtypes',
 --- | 'typeHierarchy/supertypes',
---- | 'window/workDoneProgress/cancel',
 --- | 'workspaceSymbol/resolve',
 --- | 'workspace/diagnostic',
---- | 'workspace/didChangeConfiguration',
---- | 'workspace/didChangeWatchedFiles',
---- | 'workspace/didChangeWorkspaceFolders',
---- | 'workspace/didCreateFiles',
---- | 'workspace/didDeleteFiles',
---- | 'workspace/didRenameFiles',
 --- | 'workspace/executeCommand',
 --- | 'workspace/symbol',
 --- | 'workspace/textDocumentContent',
@@ -696,15 +677,35 @@ end
 --- | 'workspace/willDeleteFiles',
 --- | 'workspace/willRenameFiles',
 
---- @alias vim.lsp.protocol.Method.ServerToClient
+--- @alias vim.lsp.protocol.Method.ClientToServer.Notification
+--- | '$/setTrace',
+--- | 'exit',
+--- | 'initialized',
+--- | 'notebookDocument/didChange',
+--- | 'notebookDocument/didClose',
+--- | 'notebookDocument/didOpen',
+--- | 'notebookDocument/didSave',
+--- | 'textDocument/didChange',
+--- | 'textDocument/didClose',
+--- | 'textDocument/didOpen',
+--- | 'textDocument/didSave',
+--- | 'textDocument/willSave',
+--- | 'window/workDoneProgress/cancel',
+--- | 'workspace/didChangeConfiguration',
+--- | 'workspace/didChangeWatchedFiles',
+--- | 'workspace/didChangeWorkspaceFolders',
+--- | 'workspace/didCreateFiles',
+--- | 'workspace/didDeleteFiles',
+--- | 'workspace/didRenameFiles',
+
+--- @alias vim.lsp.protocol.Method.ClientToServer
+--- | vim.lsp.protocol.Method.ClientToServer.Request
+--- | vim.lsp.protocol.Method.ClientToServer.Notification
+
+--- @alias vim.lsp.protocol.Method.ServerToClient.Request
 --- | 'client/registerCapability',
 --- | 'client/unregisterCapability',
---- | '$/logTrace',
---- | 'telemetry/event',
---- | 'textDocument/publishDiagnostics',
---- | 'window/logMessage',
 --- | 'window/showDocument',
---- | 'window/showMessage',
 --- | 'window/showMessageRequest',
 --- | 'window/workDoneProgress/create',
 --- | 'workspace/applyEdit',
@@ -718,6 +719,17 @@ end
 --- | 'workspace/textDocumentContent/refresh',
 --- | 'workspace/workspaceFolders',
 
+--- @alias vim.lsp.protocol.Method.ServerToClient.Notification
+--- | '$/logTrace',
+--- | 'telemetry/event',
+--- | 'textDocument/publishDiagnostics',
+--- | 'window/logMessage',
+--- | 'window/showMessage',
+
+--- @alias vim.lsp.protocol.Method.ServerToClient
+--- | vim.lsp.protocol.Method.ServerToClient.Request
+--- | vim.lsp.protocol.Method.ServerToClient.Notification
+
 --- @alias vim.lsp.protocol.Method
 --- | vim.lsp.protocol.Method.ClientToServer
 --- | vim.lsp.protocol.Method.ServerToClient