CDS dump should not warn about hidden classes

Since JDK-8247536, hidden classes are created in an normal operations while running "java -Xshare:dump". These warning are confusing and should be changed to the debug log level instead.

$ java -Xshare:dump
[0.498s][warning][cds] Skipping jdk/internal/misc/CDS$$Lambda$1+0x800000001: Hidden class
[0.498s][warning][cds] Skipping java/lang/invoke/LambdaForm$MH+0x800000002: Hidden class
[0.498s][warning][cds] Skipping java/lang/invoke/LambdaForm$DMH+0x80000000b: Hidden class
[0.498s][warning][cds] Skipping java/lang/invoke/LambdaForm$DMH+0x800000007: Hidden class
[0.498s][warning][cds] Skipping java/lang/invoke/LambdaForm$DMH+0x800000009: Hidden class
[0.498s][warning][cds] Skipping java/lang/invoke/LambdaForm$DMH+0x800000016: Hidden class
[0.498s][warning][cds] Skipping java/lang/invoke/LambdaForm$DMH+0x800000011: Hidden class
[0.498s][warning][cds] Skipping java/lang/invoke/LambdaForm$DMH+0x80000000d: Hidden class
[0.498s][warning][cds] Skipping java/lang/invoke/GenerateJLIClassesHelper$$Lambda$2+0x800000003: Hidden class
[0.498s][warning][cds] Skipping java/lang/invoke/GenerateJLIClassesHelper$$Lambda$3+0x800000005: Hidden class
[0.498s][warning][cds] Skipping java/lang/invoke/LambdaForm$DMH+0x800000004: Hidden class
[0.498s][warning][cds] Skipping java/lang/invoke/LambdaForm$DMH+0x800000035: Hidden class
[0.498s][warning][cds] Skipping java/lang/invoke/LambdaForm$DMH+0x80000003d: Hidden class
[0.498s][warning][cds] Skipping java/lang/invoke/LambdaForm$DMH+0x80000003b: Hidden class
[0.498s][warning][cds] Skipping java/lang/invoke/LambdaForm$DMH+0x800000038: Hidden class
[0.498s][warning][cds] Skipping java/lang/invoke/LambdaForm$DMH+0x800000060: Hidden class