RFR: 8344854: Modernize test/jdk/java/net/URLClassLoader/RemoveJar.java [v2]

[Eirik Bjørsnøs]

> Can I get a review of this test-only cleanup/speedup PR which modernizes the test `RemoveJar.java`.
> 
> This test attempts a variety of class loading scenarios on a URLClassLoader and verifies that when the loader is closed, it has released its JAR file (such that it may be deleted on Windows).
> 
> Changes in this PR include:
> 
> * Converting the test to JUnit 5
> * Making it `@Parameterized` instead of using multiple jtreg runs
> * Producing the sample class file using the ClassFile API instead calling out to `javac` via ToolProvider
> * Packaging the JAR using `JarOutputStream` instead of calling out to the `jar` tool.
> * Adding some code and method comments to support understading of what this test does and why 
> 
> A nice benefit of this change is that it speeds up the runtime from ~15 seconds to ~1 second on my laptop.
> 
> Unfortunately, this test relies on Windows to fail, that is something I plan to look into separately.
> 
> Verification: GHA tests pending. (No local Windows dev environment)

Eirik Bjørsnøs has updated the pull request incrementally with one additional commit since the last revision:

  Sanity check that the JarFileFactory caches are unpopulated at start of a test run

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/22319/files
  - new: https://git.openjdk.org/jdk/pull/22319/files/b49bc034..5d0be877

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=22319&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=22319&range=00-01

  Stats: 24 lines in 1 file changed: 20 ins; 3 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/22319.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22319/head:pull/22319

PR: https://git.openjdk.org/jdk/pull/22319