[jdk21u-dev] RFR: 8309763: Move tests in test/jdk/sun/misc/URLClassPath directory to test/jdk/jdk/internal/loader

[Goetz Lindenmaier]

I backport this for parity with 21.0.4-oracle.

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Commit messages:
 - Backport 57fc9a3e968cafe3b618a216630e703a39d5676e

Changes: https://git.openjdk.org/jdk21u-dev/pull/318/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=318&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8309763
  Stats: 0 lines in 5 files changed: 0 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/318.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/318/head:pull/318

PR: https://git.openjdk.org/jdk21u-dev/pull/318