RFR: 8319324: FFM: Reformat javadocs

[Per Minborg]

This PR proposes to reformat all the JavaDocs for the FFM API. This would bring the FFM API docs more in line with the existing Java documentation (see below).  Occasional drive-by fixes are also included in this PR (such as spelling and capitalization).

I am aware this PR will (if approved) make a significant mark in the change logs which is regrettable.

Background:

Older classes like `Object` and `List` have a maximum line length of 80 characters whereas newer classes like `ScopedValue` have a maximum line length of 90 characters.

The FFM API currently has javadoc lines that exceed 135 characters per line. It is also customary to use double spaces when starting a new sentence.

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Commit messages:
 - Reformat javadocs
 - FFM: Harmonize the @throws tags in the javadocs
 - Merge branch 'master' into javadoc-throws
 - Harmonize some of the javadoc throws

Changes: https://git.openjdk.org/jdk/pull/16518/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16518&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8319324
  Stats: 2970 lines in 15 files changed: 850 ins; 11 del; 2109 mod
  Patch: https://git.openjdk.org/jdk/pull/16518.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16518/head:pull/16518

PR: https://git.openjdk.org/jdk/pull/16518