Remove uses of records in datalog/schema

[langston-barrett]

There are a few record types in datalog/schema:

phi-instr.dl
9:.type PhiInstructionPair = [

switch-instr.dl
10:.type SwitchInstructionCase = [

landingpad-instr.dl
129:.type Clause = [

These don't seem to provide value above and beyond a version that doesn't use records. Indeed, most (all?) come with auxiliary relations that simply convert them to non-record forms.

These seem tied up with the only relations coming out of the FactGenerator with names that start with underscores (see #42).