Don't send info output to stderr

[clason]

LanguageServer.jl (and some of its dependent packages) send (all?!) info output (such as the timing summary or the packages loaded from cache) to stderr, which leads to quickly ballooning log files in clients such as Neovim since these messages are treated as actual errors.

As these are not error messages, they should be emitted accordingly (stdout, or ideally as actual LSP notifications).