RFR: 8310643: Misformatted copyright messages in FFM [v2]

[Per Minborg]

> This PR suggests updating some of the ill-formed copyright headers in the FFM API and the implementation and test thereof.
> 
> Some of the test files will have now the "classpath" exception. Is this correct?

Per Minborg has updated the pull request incrementally with two additional commits since the last revision:

 - Remove classpath exception from test files
 - Add classpath exception to some internal files

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/15042/files
  - new: https://git.openjdk.org/jdk/pull/15042/files/3389537c..d81d0c4e

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15042&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15042&range=00-01

  Stats: 135 lines in 45 files changed: 8 ins; 82 del; 45 mod
  Patch: https://git.openjdk.org/jdk/pull/15042.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15042/head:pull/15042

PR: https://git.openjdk.org/jdk/pull/15042