RFR: 8287843: File::getCanonicalFile doesn't work for \?\C:\ style paths DOS device paths [v5]

[Brian Burkhalter]

> In the Windows implementation of java.io.File.getCanonicalPath, strip any long path or UNC prefix before canonicalizing the remainder of the pathname.

Brian Burkhalter has updated the pull request incrementally with three additional commits since the last revision:

 - 8287843: Strip prefix in more methods; remove bad test case
 - 8287843: Add WindowsPrefixes test
 - 8287843: Convert GetAbsolutePath and IsAbsolute tests to JUnit and add some test cases

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Changes:
  - all: https://git.openjdk.org/jdk/pull/15603/files
  - new: https://git.openjdk.org/jdk/pull/15603/files/2ea422c1..63e2c5c2

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15603&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15603&range=03-04

  Stats: 219 lines in 5 files changed: 143 ins; 13 del; 63 mod
  Patch: https://git.openjdk.org/jdk/pull/15603.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15603/head:pull/15603

PR: https://git.openjdk.org/jdk/pull/15603