Properly Implement the Simplified Syntax about squid HOT 1 CLOSED

There used to be a "simple" alternative to the "contextual" quasiquote system, but this turned out to complicate everything and require duplicating internal implementations, without actually bringing anything really useful to the table.

The new way of doing things if one doesn't care about contexts is to use OpenCode (which can be renamed on import; see this test case), and to use explicit unsafe_asClosedCode casts before calling operations like run and compile, which require an empty context, or on the RHS of a rewriting if the context doesn't match.

from squid.