RFR: 8338731: MemoryLayout::offsetHandle can return a negative offset

[Maurizio Cimadamore]

When working on startup improvements, I noticed that the method handle returned by `MemoryLayout::offsetHandle` can overflow if the client calls the handle with a base offset that is too big.

In other similar situations, the layout API always fails with `ArithmeticException` (see `MemoryLayout::scale`), so we should do the same here.

The fix is to use a `Math::addExact(long, long)` for the outermost add operation in the computation of the offset method handle. That outermost computation in fact is the only one that can overflow: it is an addition between a user-provided base offset `B` and a layout offset `L`. `L` is guaranteed not to overflow, by construction (as `L` is derived from a layout path). But `B` + `L` might overflow, so the new logic checks for that.

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Commit messages:
 - Initial push

Changes: https://git.openjdk.org/jdk/pull/20662/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20662&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8338731
  Stats: 23 lines in 3 files changed: 14 ins; 1 del; 8 mod
  Patch: https://git.openjdk.org/jdk/pull/20662.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20662/head:pull/20662

PR: https://git.openjdk.org/jdk/pull/20662