Migrate data folder creation to core

[pgayvallet]

The data folder creation is currently done from the kibana legacy plugin

kibana/src/legacy/core_plugins/kibana/index.js

Lines 47 to 57 in d1a6fa2

	preInit: async function (server) {
	try {
	// Create the data directory (recursively, if the a parent dir doesn't exist).
	// If it already exists, does nothing.
	await mkdirAsync(server.config().get('path.data'), { recursive: true });
	} catch (err) {
	server.log(['error', 'init'], err);
	// Stop the server startup with a fatal error
	throw err;
	}
	},

we need to move this to core

[pgayvallet]

I'm unsure where this folder creation should be performed. I could create a data or a path service, but that feel like overkill to add a service just to perform a mkdir... Would putting that directly in src/core/server/server.ts be acceptable?