Read global ratoml before first config query

[alibektas]

          Given https://github.com/rust-lang/rust-analyzer/pull/17246, it's still not being read early enough -- there is a pretty big chicken/egg problem with configs like this:

[workspace.discoverConfig]
...

We don't read rust-analyzer.toml until workspaces have already been discovered (to find the root), and we can't discover a workspace because haven't read it. I think we need to search upwards from the current working directory to find a rust-analyzer.toml to use on startup.

For rust-analyzer.toml users, these configs will never be populated in src/bin/main.rs:

rust-analyzer/crates/rust-analyzer/src/bin/main.rs

Lines 268 to 273 in f46af90

	if config.discover_workspace_config().is_none()
	&& !config.has_linked_projects()
	&& config.detached_files().is_empty()
	{
	config.rediscover_workspaces();
	}

Originally posted by @cormacrelf in #17661 (comment)

[alibektas]

This will be waiting for #17537 to be implemented first, as it has a certain relevance in terms of project discovery.