[jdk17u-dev] RFR: 8272908: Missing coverage for certain classes in com.sun.org.apache.xml.internal.security

[Martin Doerr]

Clean backport of [JDK-8272908](https://bugs.openjdk.java.net/browse/JDK-8272908)

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Commit messages:
 - Backport a16f2d0a3c326dd8b3b2133a9c170d998b7aa631

Changes: https://git.openjdk.java.net/jdk17u-dev/pull/309/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk17u-dev&pr=309&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8272908
  Stats: 253 lines in 3 files changed: 246 ins; 0 del; 7 mod
  Patch: https://git.openjdk.java.net/jdk17u-dev/pull/309.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk17u-dev pull/309/head:pull/309

PR: https://git.openjdk.java.net/jdk17u-dev/pull/309