RFR: 8331467: FileSystems.getDefault fails with ClassNotFoundException if custom default provider is in run-time image [v8]

[liyazzi]

> For two cases:
> 
> 1. When the ImageReaderFactory was loaded by local jdk,that means the ImageReaderFactory was loaded by boot class loader,then init the `Path BOOT_MODULES_JIMAGE` by using `sun.nio.fs.DefaultFileSystemProvider` which is obtained through reflection,due to it is in jdk internal.
> 2. When loaded by a target jdk, such as jdk8 runtime, then use the Java 8 compatible APIs: `FileSystems.getDefault()` to init the `BOOT_MODULES_JIMAGE` field.
> Then we can avoid the circular dependencies in class loading caused by loading the defaultSystemProvider.

liyazzi has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 17 commits:

 - Enable the 'testFspInRuntimeImage' test in SetDefaultProvider
 - Merge branch 'master' of github.com:liyazzi/jdk into 8331467
 - revert the SetDefaultProvider
 - Merge branch 'openjdk:master' into 8331467
 - add test case in test/jdk/java/nio/file/spi/SetDefaultProvider.java as the test of this issue
 - add '\s' to avoid trailing whiteSpace
 - empty commit
 - remove the '\s' and trailing whitespace
 - add test.jdk value log
 - deal with trailing whitespace
 - ... and 7 more: https://git.openjdk.org/jdk/compare/23d6f747...ebf6b1da

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Changes: https://git.openjdk.org/jdk/pull/22628/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=22628&range=07
  Stats: 22 lines in 2 files changed: 17 ins; 2 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/22628.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22628/head:pull/22628

PR: https://git.openjdk.org/jdk/pull/22628