Improvements for Xtrace String printing feature

[paulcheeseman]

Suggested improvements for the new Xtrace String printing feature introduced for #16416:

First, this references for String objects are still shown only as addresses. For example on the first and second lines here:

14:47:13.242*0x21f00              mt.0         > java/lang/String.concat(Ljava/lang/String;)Ljava/lang/String; bytecode method, this = 0x60383cfd0
14:47:13.242 0x21f00              mt.18         - this: java/lang/String@000000060383CFD0 method arguments: ((String)"java.base")
14:47:13.242 0x21f00              mt.6         < java/lang/String.concat(Ljava/lang/String;)Ljava/lang/String; bytecode method
14:47:13.243 0x21f00              mt.28        - return value: (String)"/java.base"

It would be great to see String contents for this references as well.

Second, the Strings' contents are now printed instead of their addresses, but there are situations where having both would be useful - for example, if you wanted to locate the String objects in a dump that was taken alongside the trace.

Finally, would it be possible to print the contents of char[] instances (and maybe even byte[]) in the same way? A text representation of a byte[] (e.g. interpreting each byte as an ASCII codepoint) wouldn't always be useful, but there are definitely times when it would be.

[tajila]

@h3110n3rv3 Please address the concersn regarding Strings being used as a receiver for method calls (It would be great to see String contents for this references as well).

[tajila]

We can look at char[] and byte[] in a separate PR.