Add some commands

[Fuco1]

• lsp-mssql-cancel to cancel current query
• ~lsp-mssql-format-region to format the region~ this is already by default in lsp-mode

I also changed various display/pop commands to use display-buffer which is user-configurable via display-buffer-alist. For example, I have multiple monitors and I want the result set to be shown (not selected) on the second one if the window is already visible there, such that I can keep editing the queries without having to switch back-and-forth between windows.

[yyoncho]

I added you as a maintainer. Feel free to push the trivial PRs directly.