[foreign-memaccess+abi] RFR: 8314071: Test java/foreign/TestByteBuffer.java timed out [v2]

[Per Minborg]

> This PR proposes improving performance for two `VarHandle` objects and increasing the timeout for the tests.

Per Minborg has updated the pull request incrementally with one additional commit since the last revision:

  Reduce the LARGE_SIZE to 2.5 GiB

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Changes:
  - all: https://git.openjdk.org/panama-foreign/pull/866/files
  - new: https://git.openjdk.org/panama-foreign/pull/866/files/473e466c..957c7e73

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=panama-foreign&pr=866&range=01
 - incr: https://webrevs.openjdk.org/?repo=panama-foreign&pr=866&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/panama-foreign/pull/866.diff
  Fetch: git fetch https://git.openjdk.org/panama-foreign.git pull/866/head:pull/866

PR: https://git.openjdk.org/panama-foreign/pull/866