RFR: JDK-8301990: Separate Arguments::parse into two phases

[Justin King]

Separate out some logic from `Arguments::parse` into a separate preceding phase, preprocessing. See JDK-8301990 and JDK-8299196 for more details.

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Commit messages:
 - Fix refactoring mistake
 - Separate Arguments::parse into two phases

Changes: https://git.openjdk.org/jdk/pull/12458/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12458&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8301990
  Stats: 135 lines in 3 files changed: 79 ins; 8 del; 48 mod
  Patch: https://git.openjdk.org/jdk/pull/12458.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12458/head:pull/12458

PR: https://git.openjdk.org/jdk/pull/12458