RFR: 8354053: Remove unused JavaIOFilePermissionAccess

[Roger Riggs]

The JavaIOFilePermissionAccess interface is removed from SharedSecrets and its implementation (FilePermCompat.java) used by the test is moved to java.io FilePermission where cross package access is not needed. 
The test FilePermissionCollectionMerge is updated to access the internal implementation in FilePermission. 
Modernized the initialization from the system property `jdk.io.permissionsUseCanonicalPath`. 
The remaining support will be removed when FilePermission is removed.

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Commit messages:
 - 8354053: Remove unused JavaIOFilePermissionAccess

Changes: https://git.openjdk.org/jdk/pull/24603/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24603&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8354053
  Stats: 262 lines in 5 files changed: 59 ins; 176 del; 27 mod
  Patch: https://git.openjdk.org/jdk/pull/24603.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24603/head:pull/24603

PR: https://git.openjdk.org/jdk/pull/24603