RFR: 8286390: Address possibly lossy conversions in jdk.incubator.foreign moved to java.base

[Jorn Vernee]

Address possible lossy conversion warning in `ProgrammableInvoker`.

Testing: `run-test-jdk_foreign`, testing with patch from https://github.com/openjdk/jdk/pull/8599 to see if the warning is gone.

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Commit messages:
 - Address possible lossy conversion warning in ProgrammableInvoker

Changes: https://git.openjdk.java.net/jdk/pull/8697/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8697&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8286390
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8697.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8697/head:pull/8697

PR: https://git.openjdk.java.net/jdk/pull/8697