Previously the dialects registered were fixed per LSP binary. This works
as long as all the dialects of interest from the different projects
across which one uses the LSP, are disjoint. This expands this to
support cases where there are dialects that overlap in dialect name but
usage of these are separate wrt projects. The alternative is multiple
binaries and switching LSP used in editor per project (there is some
extra complexity in hosted instances).
This handles a simple (I believe common case) where one can determine
based on path and have single binary - the cost of dynamically doing so
based on path would be either keeping different registries to return or
repopulating dialect & extension maps.
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