Improvements to Java analysis

The following changes in version 1.22 affect Java analysis in all applications.

Changes to existing queries

Query	Expected impact	Change
Equals method does not inspect argument type (`java/unchecked-cast-in-equals`)	Fewer false positive and more true positive results	Precision has been improved by doing a bit of inter-procedural analysis and relying less on ad-hoc method names.
Uncontrolled data in arithmetic expression (`java/uncontrolled-arithmetic`)	Fewer false positive results	Precision has been improved in several ways, in particular, by better detection of guards along the data-flow path.
Uncontrolled data used in path expression (`java/path-injection`)	Fewer false positive results	The query no longer reports results guarded by `!var.contains("..")`.
User-controlled data in arithmetic expression (`java/tainted-arithmetic`)	Fewer false positive results	Precision has been improved in several ways, in particular, by better detection of guards along the data-flow path.

The virtual dispatch library has been updated to give more precise dispatch targets for Object.toString() calls. This affects all security queries and removes false positive results that arose from paths through impossible toString() calls.
The library VCS.qll and all queries that imported it have been removed.
The second copy of the interprocedural TaintTracking library has been renamed from TaintTracking::Configuration2 to TaintTracking2::Configuration, and the old name is now deprecated. Import semmle.code.java.dataflow.TaintTracking2 to access the new name.
The data-flow library now makes it easier to specify barriers/sanitizers arising from guards by overriding the predicate isBarrierGuard/isSanitizerGuard on data-flow and taint-tracking configurations respectively.
The possibility of specifying barrier edges using isBarrierEdge/isSanitizerEdge in data-flow and taint-tracking configurations has been replaced with the option of specifying in- and out-barriers on nodes by overriding isBarrierIn/isSanitizerIn and isBarrierOut/isSanitizerOut. This should be simpler to use effectively, as it does not require knowledge about the actual edges used internally by the library.