When there is flow in/out of a block through a captured variable, we can restrict
the calls that give rise to the flow to the method calls to which the blocks
belong.
String summaries that are identified by name only should not specify
value-preserving flow as this can cause spurious flow in cases where
they are applied to different but identically-named methods.
Some String methods are named identically to Array methods, and this
leads to overlapping flow summaries. These adversely affect the original
Array flow summaries.
