RFR: 8287843: File::getCanonicalFile doesn't work for \?\C:\ style paths DOS device paths [v4]

[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 one additional commit since the last revision:

  8287843: Move prefix stripping to separate method; add to isAbsolute

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Changes:
  - all: https://git.openjdk.org/jdk/pull/15603/files
  - new: https://git.openjdk.org/jdk/pull/15603/files/a8726fbb..2ea422c1

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15603&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15603&range=02-03

  Stats: 42 lines in 1 file changed: 31 ins; 7 del; 4 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