Also needed to fix up `TestUtil/UnresolvedCalls.qll` after a bad merge
conflict resolution. Since all calls are now DataFlowCall, and not JUST
the ones that can be resolved, we need to put in the restriction that
the callable can also be resolved.
This commit used to make sense to have here in the ordering of commits,
but due to various rebases it no longer changes any test output..
it's still a good change though, so I'll keep it.
- "Normal" instead of "NonSpecial"
- "NonLibrary" instead of "2"
I could not find a good replacement for "NonLibrary", nor for "Source",
but I added QLDocs in a few places to help the reading.
- add `getCallable`, `getArg` and `getNode`
- these are `none` for summary calls
- revert "external" uses (they had been changed to `DataFlowSourceCall`)
- Branch predicates are made simple. In particular, they do not try to detect library calls.
- All branches based on `CallNode`s are gathered into one.
- That branch has been given a class `NonSpecialCall`, which is the new parent of call classes based on `CallNode`s. (Those classes now have more involved charpreds.)
- A new such class, 'LambdaCall` has been split out from `FunctionCall` to allow the latter to replace its
general `CallNode` field with a specific `FunctionValue` one.
- `NonSpecialCall` is not an abstract class, but it has some abstract overrides. Therefor, it is not
considered a resolved call in the test `UnresolvedCalls.qll`.
