RFR: 7820: Add validations for master password [v2]

[Suchita Chaturvedi]

> This PR adds password validations for master password field.

Suchita Chaturvedi has updated the pull request incrementally with one additional commit since the last revision:

  Added Junit test cases and moved the logic to common util file

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Changes:
  - all: https://git.openjdk.org/jmc/pull/406/files
  - new: https://git.openjdk.org/jmc/pull/406/files/6e709d4f..10d0e54a

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jmc&pr=406&range=01
 - incr: https://webrevs.openjdk.org/?repo=jmc&pr=406&range=00-01

  Stats: 81 lines in 3 files changed: 71 ins; 8 del; 2 mod
  Patch: https://git.openjdk.org/jmc/pull/406.diff
  Fetch: git fetch https://git.openjdk.org/jmc pull/406/head:pull/406

PR: https://git.openjdk.org/jmc/pull/406