RFR: 8322847: java.lang.classfile.BufWriter should specify @throws for its writeXXX methods

[Adam Sotona]

This patch adds missing `@throws` javadoc annotations to `java.lang.classfile.BufWriter`.

Please review.

Thank you,
Adam

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Commit messages:
 - 8322847: java.lang.classfile.BufWriter should specify @throws for its writeXXX methods

Changes: https://git.openjdk.org/jdk/pull/18913/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18913&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8322847
  Stats: 7 lines in 1 file changed: 5 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/18913.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18913/head:pull/18913

PR: https://git.openjdk.org/jdk/pull/18913