RFR: 8301063: Remove dead code from GrowableArray

[Tobias Hartmann]

While looking for a method to truncate a GrowableArray, I noticed that there are both `trunc_to` and `truncate_to` while the behavior of the latter is confusing. Since it's unused, I propose to remove it (together with `data_size_in_bytes` which is also unused). The `truncate_to` and `truncate_from` methods were added by [JDK-8271515](https://bugs.openjdk.org/browse/JDK-8271515) and were unused right from the beginning. `data_size_in_bytes` was introduced by [JDK-8254231](https://bugs.openjdk.org/browse/JDK-8254231) and became unused after [JDK-8283689](https://bugs.openjdk.org/browse/JDK-8283689).

Thanks,
Tobias

-------------

Commit messages:
 - 8301063: Remove dead code from GrowableArray

Changes: https://git.openjdk.org/jdk/pull/12191/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12191&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8301063
  Stats: 15 lines in 1 file changed: 0 ins; 15 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/12191.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12191/head:pull/12191

PR: https://git.openjdk.org/jdk/pull/12191