RFR: Slightly simpler way of waiting for a specific time

[kabutz]

Instead of writing the logic for calling System.nanoTime() etc. ourselves, could we perhaps use awaitNanos() instead?

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Commit messages:
 - Slightly simpler way of waiting for a specific time

Changes: https://git.openjdk.java.net/loom/pull/19/files
 Webrev: https://webrevs.openjdk.java.net/?repo=loom&pr=19&range=00
  Stats: 3 lines in 1 file changed: 0 ins; 2 del; 1 mod
  Patch: https://git.openjdk.java.net/loom/pull/19.diff
  Fetch: git fetch https://git.openjdk.java.net/loom pull/19/head:pull/19

PR: https://git.openjdk.java.net/loom/pull/19