RFR: 8297757: VarHandles.getStaticFieldFromBaseAndOffset should get the receiver type from VarHandle

[Mandy Chung]

`VarHandles.getStaticFieldFromBaseAndOffset` maps a base/offset/fieldType to a static `Field`.   It's fragile to assume that the location of a static field returned by `Unsafe.staticFieldBase` is a Class object.    This changes the VarHandle implementation for static fields (i.e. `FieldStaticReadOnly` and `FieldStaticReadWrite` classes) to include the receiver type in addition to the base and offset.

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Commit messages:
 - 8297757: Re-examine assumption in VarHandles.getStaticFieldFromBaseAndOffset that base is a Class object

Changes: https://git.openjdk.org/jdk/pull/12100/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12100&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8297757
  Stats: 36 lines in 2 files changed: 3 ins; 2 del; 31 mod
  Patch: https://git.openjdk.org/jdk/pull/12100.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12100/head:pull/12100

PR: https://git.openjdk.org/jdk/pull/12100