RFR: JDK-8294994: Update Jarsigner and Keytool i18n tests to validate i18n compliance [v2]

[Bill Huang]

> The jarsigner and keytool are localized into English, German, Japanese and Simplified Chinese. This task is to modify the existing i18n tests to validate i18n compliance in these tools. 
> 
> In addition, this task also contains changes for manual test enhancement and simplification which originated from [JDK-8292663](https://bugs.openjdk.org/browse/JDK-8292663.

Bill Huang has updated the pull request incrementally with one additional commit since the last revision:

  Implemented review comments.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/10635/files
  - new: https://git.openjdk.org/jdk/pull/10635/files/7812f3c4..a36cd005

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10635&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10635&range=00-01

  Stats: 203 lines in 2 files changed: 113 ins; 78 del; 12 mod
  Patch: https://git.openjdk.org/jdk/pull/10635.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10635/head:pull/10635

PR: https://git.openjdk.org/jdk/pull/10635