CastBuilder refactoring: inner classes moved to separate package

...cle/truffle/r/nodes/builtin/base/ConnectionFunctions.java

...c/com/oracle/truffle/r/nodes/builtin/CastBuilderTest.java

.../oracle/truffle/r/nodes/test/PipelineToCastNodeTests.java

.../com/oracle/truffle/r/nodes/test/RBuiltinDiagnostics.java

...s/src/com/oracle/truffle/r/nodes/builtin/CastBuilder.java

...cle/truffle/r/nodes/builtin/casts/PipelineToCastNode.java

.../truffle/r/nodes/builtin/casts/fluent/ArgCastBuilder.java

...le/truffle/r/nodes/builtin/casts/fluent/ChainBuilder.java

...fle/r/nodes/builtin/casts/fluent/CoercedPhaseBuilder.java

...le/r/nodes/builtin/casts/fluent/FindFirstNodeBuilder.java

...ruffle/r/nodes/builtin/casts/fluent/HeadPhaseBuilder.java

...fle/r/nodes/builtin/casts/fluent/InitialPhaseBuilder.java

...truffle/r/nodes/builtin/casts/fluent/PipelineBuilder.java

...e/r/nodes/builtin/casts/fluent/PipelineConfigBuilder.java

.../r/nodes/builtin/casts/fluent/PreinitialPhaseBuilder.java

...odes/src/com/oracle/truffle/r/nodes/unary/BypassNode.java