[foreign-memaccess+abi] RFR: 8265185: make sure all code snippets in jdk.incubator.foreign javadoc comments are proper

[Athijegannathan Sundararajan]

checked by compiling code snippets

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Commit messages:
 - 8265185: make sure all code snippets in jdk.incubator.foreign javadoc comments are proper

Changes: https://git.openjdk.java.net/panama-foreign/pull/501/files
 Webrev: https://webrevs.openjdk.java.net/?repo=panama-foreign&pr=501&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8265185
  Stats: 46 lines in 8 files changed: 3 ins; 0 del; 43 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/501.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/501/head:pull/501

PR: https://git.openjdk.java.net/panama-foreign/pull/501