[jdk17] RFR: JDK-8268826: Cleanup Override in Context-Specific Deserialization Filters [v3]

[Roger Riggs]

> Remove the unnecessary special case "OVERRIDE" in jdk.serialFilterFactory property.
> Fix description in the example of a filter allowing platform classes.
> Suppress some warnings about use of SecurityManager in tests.

Roger Riggs has updated the pull request incrementally with one additional commit since the last revision:

  Simplify error case handling during filter factory initialization
  by ensuring that Config.setSerialFilterFactory throws IllegalStateException
  if called as a side effect of class loading and initialization.

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Changes:
  - all: https://git.openjdk.java.net/jdk17/pull/85/files
  - new: https://git.openjdk.java.net/jdk17/pull/85/files/0add8a1c..cf6f5edb

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk17&pr=85&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk17&pr=85&range=01-02

  Stats: 16 lines in 1 file changed: 2 ins; 9 del; 5 mod
  Patch: https://git.openjdk.java.net/jdk17/pull/85.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk17 pull/85/head:pull/85

PR: https://git.openjdk.java.net/jdk17/pull/85