RFR: 7820: Add validations for master password [v3]

[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:

  Implemented review comments

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Changes:
  - all: https://git.openjdk.org/jmc/pull/406/files
  - new: https://git.openjdk.org/jmc/pull/406/files/10d0e54a..ba4bbfa3

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jmc&pr=406&range=02
 - incr: https://webrevs.openjdk.org/?repo=jmc&pr=406&range=01-02

  Stats: 39 lines in 4 files changed: 30 ins; 6 del; 3 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