RFR: 8264539: Improve failure message of java/nio/file/WatchService/SensitivityModifier.java [v2]

[Brian Burkhalter]

> Please consider this request to improve the message printed when no `ENTRY_MODIFY` events are received. In the polling implementation of `WatchService` currently used on macOS, it would be useful to know the sensitivity of polling in effect for the failing case. It might indicate, for example, that low sensitivity should not be used in the test.

Brian Burkhalter has updated the pull request incrementally with one additional commit since the last revision:

  8264539: Change poll timeout on macOS; use RandomFactory

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/3290/files
  - new: https://git.openjdk.java.net/jdk/pull/3290/files/708e9d6a..bc8f9504

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=3290&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=3290&range=00-01

  Stats: 16 lines in 1 file changed: 8 ins; 0 del; 8 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3290.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3290/head:pull/3290

PR: https://git.openjdk.java.net/jdk/pull/3290