RFR: 8231107: Allow store password to be null when saving a PKCS12 KeyStore [v4]

[Weijun Wang]

> You can create a password-less PKCS12 KeyStore file now by calling `ks.store(outStream, null)` no matter what the default cert protection algorithm and Mac algorithm are defined in `java.security`.
> 
> Note: the system properties set in `ToolsJDK.gmk` to generate `cacerts` must be retained (at the moment) because the tool is launched with BOOT_JDK.

Weijun Wang has updated the pull request incrementally with one additional commit since the last revision:

  same spec in SPI

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/5950/files
  - new: https://git.openjdk.java.net/jdk/pull/5950/files/3670f992..266cf6de

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=5950&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=5950&range=02-03

  Stats: 3 lines in 1 file changed: 2 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5950.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5950/head:pull/5950

PR: https://git.openjdk.java.net/jdk/pull/5950