Add tests for the Stim compiler

[orpuente-MS]

Categories of tests covered by this PR:

Lexer

• Int and Float Numeric literals generate the right Tokens
• leading newlines at beginning of file work fine
• trailing newlines at end of file work fine
• newlines in between instructions work fine
• Comments work fine
• Instruction name is lexed correctly
• Single char token is lexed correctly
• Rec / Sweep / Tag are lexed correctly
• Unrecognized characters error works

Parser

• Instruction arguments parse correctly
• Instruction tags parse correctly
• Instruction targets parse correctly
• Instruction shapes parse correctly (with / without args, tags, targets)
• Blocs parse correctly
• Newlines parse correctly, comments don't interfere with parser
• Numbers are parsed correctly (both uint and doubles)
• General errors are generated correctly
• Span is correct
• Edge cases

QIR Codegen

Gates

• single-qubit gates generate correct QIR
• single-qubit gates with broadcasting generate correct QIR
• two-qubit gates generate correct QIR
• two-qubit gates with broadcasting generate correct QIR
• two-qubit gates with odd number of targets yield error messages
• unsupported gates yield error messages

Noise Channels

• Noise channels get compiled to the right NoiseConfig object
• single-qubit error channels generate correct QIR
• single-qubit error channels with broadcasting generate correct QIR
• two-qubit error channels generate correct QIR
• two-qubit error channels with broadcasting generate correct QIR
• two-qubit error channels with odd number of targets yield error messages
• I_ERROR and II_ERROR work without paren arguments
• the rest of error channels without paren arguments yield error messages

Preselect

• preselect_expect with a previous preselect_begin generates correct QIR
• multiple preselect_expect generate correct QIR
• preselect_expect without a previous preselect_begin yields an error message