NullAway 0.12.15

NullAway now includes a BOM artifact com.uber.nullaway:nullaway-bom. Otherwise, this release contains a few bug
fixes and improvements to JSpecify support.

• Fix URL for RequireExplicitNullMarking checker (#1369)
• Handle annotations on type variables in return and field types (#1371)
• Change how recursive calls to dataflow are detected (#1374)
• JSpecify: use type on identifier when its type is a type variable (#1378)
• Include method type parameters in astubx files. by @haewiful (#1370)
• Create nullaway-bom project (#1130) by @lpireyn (#1380)
• Run dataflow analysis on bodies of lambdas passed to generic methods (#1375)
• Maintenance
  • Remove BaseNoOpHandler and replace with default methods in Handler (#1376)