[CS] Connect isolated conjunctions to referenced VarDecls
Currently we only consider ParamDecls, but isolated
conjunctions can reference external VarDecls too.
This fixes a spurious "cannot reference invalid declaration"
error when the result builder transform is disabled
in the test case rdar104687668.swift. It also fixes
the attached test case, where an if expression
references a pattern var in a for loop.
rdar://105080067
