implementing Interprocedural Dataflow

[SchWiniX]

This PR implements the interpersonal dataflow strategy presented in my thesis.
The implementation consists of the following main components:

• FCallEmbedder/FCallStrategy: Main driver for embedding functions into leaf functions; uses the strategy pattern for ease of use. This can be controlled by the --Xdataflow-strategy flag.
• Rewrite Engine: Block mutator used to both diversify and introduce the interprocedural dataflow.
• Pattern Matching: Used by the rewrite engine to match on statements.
• Rule/Reduce Info: Used to dump rule application information to file and input reduce information (used by RyReduce).
• VarState: Used during RySmith to dump runtime state of leaf function and in RyLink to read the same information back in.
• ModAssStmt/ModExpr: New structure in SymIR used to express modular arithmetic polynomials.
• Bitwise ops: Adds most bitwise operations for SymIR for use in both RySmith and the Rewrite Engine.
• Stmt/Block Copier: Used by the Rewrite Engine to rewrite the actual SymIR expression.
• Randfill: used in RySmith to fill unsolved symbolic values, needed since the old approach of filling all regardless of context is problematic for shift operations.

Scripts:

• New RyReduce: used to reduce the number of rule applications of a given program identified by its seed and sample number.
• --save-func flag in fuzz.py: Stores the original function set for each buggy whole program found. Needed by RyReduce to rerun whole program generation.

New RyLink flags:

• -n, --sno: only runs this sample number (i.e., skips all other samples)
• --Xcoeff-replace-proba: equivalent to the old --Xreplace-proba
• --Xdataflow-strategy: {0=literal, 1=Prime interpolating, 2=Rewrite} select for different strategies of introducing interprocedural dataflow.
• --Xinit-replace-proba: Probability of replacing an argument literal with a variable during function embedding.
• --Xvar-take-proba: Probability of selecting any given variable in an interprocedural dataflow expression.
• --Xrule-count: Maximal number of rule applications applied by the Rewrite Engine.
• --Xrule-info: Dump rule info file (used by RyReduce)
• --Xreduce-mode: Read rule info file (used by RyReduce)

Additionally, this PR introduced 1 new dependency to the Flint library