[lworld] RFR: 8348904: [lworld] Remove concept of default value object and zeroInstance [v2]

[Roger Riggs]

> Remove support for the default value object and zeroInstance, no longer included in the spec.
> In related tests, test cases were removed if no longer applicable or replaced by a hand created zero/null object.

Roger Riggs has updated the pull request incrementally with three additional commits since the last revision:

 - Remove debug println
 - Merge branch 'xx-broken-default-value-object' into 8348904-remove-default-value-object
   Remove vestigal remains of zeroInstance in DirectMethodHandle.makePreparedFieldLambdaForm.
 - 8348904: [lworld] Remove concept of default value object and zeroInstance
   Remove support for the default object and zeroInstance, no longer included in the spec.
   In related tests, test cases were removed if no longer applicable or
   replaced by a hand created zero/null object.

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

Changes:
  - all: https://git.openjdk.org/valhalla/pull/1346/files
  - new: https://git.openjdk.org/valhalla/pull/1346/files/7952b01e..483ec26f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=valhalla&pr=1346&range=01
 - incr: https://webrevs.openjdk.org/?repo=valhalla&pr=1346&range=00-01

  Stats: 11 lines in 1 file changed: 0 ins; 9 del; 2 mod
  Patch: https://git.openjdk.org/valhalla/pull/1346.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1346/head:pull/1346

PR: https://git.openjdk.org/valhalla/pull/1346