RFR: 8365558: Fix stub entry init and blob creation on Zero [v2]

[Andrew Dinn]

> Fix two problems with Zero blob/stub entry initialization:
> 1. Stop Zero allocating AdapterBlobs for the default set of i2c2i adapters even though it cannot ever use them.
> 2. Allow Zero to execute its stubgen init functions even though it is not generating code into a code buffer (i.e when blob size is declared as zero). This still allows it initialize entries to point to C functions. n.b. yhis was broken when [JDK-8359373](https://bugs.openjdk.org/browse/JDK-8359373) introduced the preuniverse Stubgen stub group.

Andrew Dinn has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains five commits:

 - set zero stubgen blob sizes to zero
 - restore error traps for zero adapter handle c2i entries
 - Merge branch 'master' into JDK-8365558
 - avoid  creating AdpaterBlobs on Zero where we cannto use them
 - Execute stubgen stub create functions even on Zero when no code expected

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Changes: https://git.openjdk.org/jdk/pull/26787/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26787&range=01
  Stats: 50 lines in 4 files changed: 30 ins; 8 del; 12 mod
  Patch: https://git.openjdk.org/jdk/pull/26787.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26787/head:pull/26787

PR: https://git.openjdk.org/jdk/pull/26787