RFR: 8242258: (jrtfs) Path::toUri throws AssertionError for malformed input

[Athijegannathan Sundararajan]

Safe URI encode logic adopted from UnixUriUtils.

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Commit messages:
 - 8242258: (jrtfs) Path::toUri throws AssertionError for malformed input

Changes: https://git.openjdk.java.net/jdk/pull/1669/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1669&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8242258
  Stats: 218 lines in 2 files changed: 206 ins; 5 del; 7 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1669.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1669/head:pull/1669

PR: https://git.openjdk.java.net/jdk/pull/1669