RFR: 8346923: MetaspaceShared base calculation may cause overflow in align_up

[Calvin Cheung]

This fix adds overflow detection in `MetaspaceShared::compute_shared_base` before calling `align_up`. It is needed in order to work with the proposed changes for [JDK-8318127](https://bugs.openjdk.org/browse/JDK-8318127) which will add an `assert` to check for overflow.

Passed tiers 1 - 4 testing.

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Commit messages:
 - 8346923: MetaspaceShared base calculation may cause overflow in align_up

Changes: https://git.openjdk.org/jdk/pull/23168/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23168&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8346923
  Stats: 48 lines in 1 file changed: 35 ins; 2 del; 11 mod
  Patch: https://git.openjdk.org/jdk/pull/23168.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23168/head:pull/23168

PR: https://git.openjdk.org/jdk/pull/23168