RFR: 8374808: Add an Instance in place of Date for KeyStore and KeyStoreSpi [v2]

[Mikhail Yankelevich]

> Hi!
> 
> This is my proposal to transfer `KeyStore` and `KeyStoreSpi` with internal implementations to use `Instance`s instead of `Date`s. 
> I would be very grateful for your comments and suggestions.
> 
> Thanks!
> 
> P.S. this is related to [JDK-8350953](https://bugs.openjdk.org/browse/JDK-8350953)

Mikhail Yankelevich has updated the pull request incrementally with one additional commit since the last revision:

  DKS tests enhanced

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/29140/files
  - new: https://git.openjdk.org/jdk/pull/29140/files/553ed938..6c35e980

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=29140&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=29140&range=00-01

  Stats: 32 lines in 1 file changed: 20 ins; 0 del; 12 mod
  Patch: https://git.openjdk.org/jdk/pull/29140.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29140/head:pull/29140

PR: https://git.openjdk.org/jdk/pull/29140