RFR: 8306560: Add TOOLING.jsh load file [v2]

[Christian Stein]

> This PR adds the `TOOLING.jsh` load file for being used in `jshell TOOLING` commands.
> 
> _Man page update is pending..._

Christian Stein has updated the pull request incrementally with one additional commit since the last revision:

  Improve help text

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Changes:
  - all: https://git.openjdk.org/jdk/pull/13609/files
  - new: https://git.openjdk.org/jdk/pull/13609/files/03e2ca7c..36eae334

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13609&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13609&range=00-01

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/13609.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13609/head:pull/13609

PR: https://git.openjdk.org/jdk/pull/13609