RFR: 8229186: Improve error messages for TestStringIntrinsics failures [v7]

[Evgeny Nikitin]

> pre-Skara RFR thread: [link](https://mail.openjdk.java.net/pipermail/hotspot-compiler-dev/2020-May/038416.html)
> 
> Error reporting was improved by writing a C-style escaped string representations for the variables passed to the
> methods being tested. For array comparisons, a dedicated diff-formatter was implemented.
> Sample output for comparing byte arrays (with artificial failure):
>  ----------System.err:(21/1553)----------
>  Result: (false) of 'arrayEqualsB' is not equal to expected (true)
>  Arrays differ starting from [index: 7]:
>  ... 5, 6,   7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, ...
>  ... 5, 6, 125, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, ...
>            ^^^^
>  java.lang.RuntimeException: Result: (false) of 'arrayEqualsB' is not
>  equal to expected (true)
>           at
>  compiler.intrinsics.string.TestStringIntrinsics.invokeAndCheckArrays(TestStringIntrinsics.java:273)
>            at ... stack trace continues - E.N.
>  Sample output for comparing char arrays:
>  ----------System.err:(21/1579)*----------
>  Result: (false) of 'arrayEqualsC' is not equal to expected (true)
>  Arrays differ starting from [index: 7]:
>  ... \\u0005, \\u0006, \\u0007, \\u0008, \\u0009, \\n, ...
>  ... \\u0005, \\u0006,      }, \\u0008, \\u0009, \\n, ...
>                      ^^^^^^^
>  java.lang.RuntimeException: Result: (false) of 'arrayEqualsC' is not
>  equal to expected (true)
>           at
>  compiler.intrinsics.string.TestStringIntrinsics.invokeAndCheckArrays(TestStringIntrinsics.java:280)
>            at
>  ... and so on - E.N.
> 
> testing: open/test/hotspot/jtreg/compiler/intrinsics/string/TestStringIntrinsics.java on linux, windows, macosx.

Evgeny Nikitin has updated the pull request incrementally with one additional commit since the last revision:

  Fix typos and comments

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/112/files
  - new: https://git.openjdk.java.net/jdk/pull/112/files/f0b1df89..d792e6d0

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=112&range=06
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=112&range=05-06

  Stats: 2 lines in 2 files changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/112.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/112/head:pull/112

PR: https://git.openjdk.java.net/jdk/pull/112