RFR: 8336675: Remove UnixFileSystemProvider.checkPath in favor of UnixPath.toUnixPath

[Andrey Turbanov]

Implementation of both methods is the same.
https://github.com/openjdk/jdk/blob/9b6f6c5c9dd6d0fbb056e8d84c3a0888a3320edf/src/java.base/unix/classes/sun/nio/fs/UnixFileSystemProvider.java#L129-L135

https://github.com/openjdk/jdk/blob/9b6f6c5c9dd6d0fbb056e8d84c3a0888a3320edf/src/java.base/unix/classes/sun/nio/fs/UnixPath.java#L172-L179

`UnixPath.toUnixPath` is already used by UnixFileSystemProvider in multiple places. Two more usages shouldn't cause problems.

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Commit messages:
 - [PATCH] Remove UnixFileSystemProvider.checkPath in favor of UnixPath.toUnixPath
 - [PATCH] Remove UnixFileSystemProvider.checkPath in favor of UnixPath.toUnixPath

Changes: https://git.openjdk.org/jdk/pull/20155/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20155&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8336675
  Stats: 21 lines in 1 file changed: 0 ins; 17 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/20155.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20155/head:pull/20155

PR: https://git.openjdk.org/jdk/pull/20155