Design DB connection string button

[artemmufazalov]

In #1367 we want to add dialog with how to connect examples.

Dialog example (it's in progress):

We need some button on Database page, that opens this dialog. It should relate both to Query and Diagnostics tabs.

Example from Yandex Query. It should be noticed, that if we open cluster domain page, domain will have nested DBs in schema tree, so button context may not be clear enough.

Current test versions: