RFR: 8336470: Source launcher should work with service loader SPI in unnamed module [v2]

[Christian Stein]

> Please review this change adding a missing resource file test to the `MemoryClassLoader::findResource` override in order to resolve all files beneath the source root path in source launch mode - analog to what was already implemented for `MemoryClassLoader::getResource`.
> 
> With this change applied, files in `META-INF/services/` are resolved; allowing services providers being supplied in source form.

Christian Stein has updated the pull request incrementally with one additional commit since the last revision:

  Add test as described in https://bugs.openjdk.org/browse/JDK-8336470

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Changes:
  - all: https://git.openjdk.org/jdk/pull/20193/files
  - new: https://git.openjdk.org/jdk/pull/20193/files/b30fa73b..d35150f2

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20193&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20193&range=00-01

  Stats: 52 lines in 3 files changed: 51 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/20193.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20193/head:pull/20193

PR: https://git.openjdk.org/jdk/pull/20193