RFR: 8276966: Improve diagnostic output for the mismatching parts of a hybrid snippet [v2]

[Hannes Wallnöfer]

> Please review a trivial change to improve the error output for hybrid snippets with mismatching inline and external snippet text.
> 
> Since the logging code drops trailing blank lines, differences in trailing whitespace were not displayed properly. See [JDK-8304408](https://bugs.openjdk.org/browse/JDK-8304408) for an example where this occurs. By adding a terminal separator we make sure trailing blank lines are not discarded. This makes it also easier to see where the snippet diff ends. 
> 
> Old output:
> 
> 
>   ----------------- inline -------------------
>   inline snippet
>   ----------------- external -----------------
>   external snippet
> 
> 
> New output:
> 
> 
>   ----------------- inline -------------------
>   inline snippet
>   ----------------- external -----------------
>   external snippet
>   --------------------------------------------

Hannes Wallnöfer has updated the pull request incrementally with one additional commit since the last revision:

  Add test

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/27621/files
  - new: https://git.openjdk.org/jdk/pull/27621/files/4b353ef9..ad95230d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27621&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27621&range=00-01

  Stats: 11 lines in 1 file changed: 8 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/27621.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27621/head:pull/27621

PR: https://git.openjdk.org/jdk/pull/27621