RFR: 8341495: JShell crashes with java.util.MissingFormatArgumentException

[Archie Cobbs]

JShell prints some of its output using `printf()` formatted strings. However, there are a few spots where a string `str` to be printed is passed directly as a format string like `format(str)` instead of indirectly like `format("%s", str)`, even though the string `str` contains unknown or arbitrary content outside of JShell's control. As a result, JShell can crash suddenly with a `MissingFormatArgumentException` or similar exception if the string `str` happens to contain a `%` format specifier, etc.

Please review this patch which attempts to fix the places where an unknown string is passed directly as a format string.

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

Commit messages:
 - Avoid invoking out.printf() with unknown format strings that might contain escapes.

Changes: https://git.openjdk.org/jdk/pull/21339/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21339&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8341495
  Stats: 58 lines in 2 files changed: 53 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/21339.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21339/head:pull/21339

PR: https://git.openjdk.org/jdk/pull/21339