Optimize CVEAssert alloca instrumentation to skip instrumenting allocas that will never be tested

[rjsmith1999]

I don't know the precise definition for all such alloca's yet.

Something like:

• address does not escape the function, is never passed to a cveassert check
  OR
• not address taken

Not address taken would be simpler to implement, the above might find more cases.

[elazaro-riverside]

To instrument alloca instructions based on their address not being taken we would need to iterate over each alloca instruction, check if any of its users are function calls, if true then instrument the alloca otherwise skip.

[elazaro-riverside]

NOTE: A pointer is considered escaped if they can be accessed outside the current program scope.

[elazaro-riverside]

This issue is connected to the current issue: #93.

[elazaro-riverside]

For testing purposes, I skipped alloca instructions that contains a single value type and are considered static (size is constant and they are located in the entry block)