Improvements on the function inference logic.

[sifislag]

Main items:

• More eagerly infer functions when two functions share their return blocks.
• Added call jump and return jump contexts in MaybeFunctionCall and IsFunctionCall
• The above made MaybeInFunctionUnderContext much more precise, in turn making IRBlockEdge more precise and removing imprecise blocks and edges from private functions.
• The context added in the function call relations allowed us to be more precise than the old costly algorithms without having to compute the costly CanReachUnderContextThroughBlock relation. The latter was removed together with the distinction between cheap and costly algorithms.
• Fixed bug causing function calls to have an incorrect number of actual args.

Added analytics:

• Analytics_InexactFunctionCallArguments
• Analytics_ReachableBlocksInTAC
• Analytics_JumpToManyWithoutGlobalImprecision

Analytics with changed definition:

• Analytics_JumpToMany
• Analytics_PolymorphicTargetSameContext as well recently