RFR: 8267338: [JVMCI] revive JVMCI API removed by JDK-8243287 [v3]

[Doug Simon]

> This PR revives ResolvedJavaType.getHostClass to preserve JVMCI compatibility. The revived method just returns `null`.

Doug Simon has updated the pull request incrementally with one additional commit since the last revision:

  fixed failing test

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/4099/files
  - new: https://git.openjdk.java.net/jdk/pull/4099/files/5bffb99a..9f8a21ef

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4099&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4099&range=01-02

  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4099.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4099/head:pull/4099

PR: https://git.openjdk.java.net/jdk/pull/4099