RFR: [type-classes] 8375482: Basic tests for UnsignedInt [v3]

[Joe Darcy]

> Add some witnesses to UnsignedInt and basic tests.

Joe Darcy has updated the pull request incrementally with one additional commit since the last revision:

  Add constants to UnsignedInt, improve tests.

-------------

Changes:
  - all: https://git.openjdk.org/valhalla/pull/1991/files
  - new: https://git.openjdk.org/valhalla/pull/1991/files/9a0e6d3d..fac238ca

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=valhalla&pr=1991&range=02
 - incr: https://webrevs.openjdk.org/?repo=valhalla&pr=1991&range=01-02

  Stats: 85 lines in 2 files changed: 84 ins; 1 del; 0 mod
  Patch: https://git.openjdk.org/valhalla/pull/1991.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1991/head:pull/1991

PR: https://git.openjdk.org/valhalla/pull/1991