RFR: some existing regression tests are failing due to universal tvars changes

[Vicente Romero]

This PR contains some type system bug fixes that were impacting existing regression tests. Improved code at Attr that deals with the `universality` of declared type variables in order to consider if primitives could be accepted as bounds in wildcards etc

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Commit messages:
 - some existing regression tests are failing due to universal tvars changes

Changes: https://git.openjdk.java.net/valhalla/pull/639/files
 Webrev: https://webrevs.openjdk.java.net/?repo=valhalla&pr=639&range=00
  Stats: 68 lines in 4 files changed: 53 ins; 4 del; 11 mod
  Patch: https://git.openjdk.java.net/valhalla/pull/639.diff
  Fetch: git fetch https://git.openjdk.java.net/valhalla pull/639/head:pull/639

PR: https://git.openjdk.java.net/valhalla/pull/639