RFR: 8354053: Remove unused JavaIOFilePermissionAccess [v2]

[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.

Roger Riggs has updated the pull request incrementally with one additional commit since the last revision:

  Simplify as suggested in review comments
  Convert static methods to instance methods and invoke on the existing FilePermission.

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/24603/files
  - new: https://git.openjdk.org/jdk/pull/24603/files/721fba81..56680c47

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=24603&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=24603&range=00-01

  Stats: 27 lines in 2 files changed: 1 ins; 2 del; 24 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