RFR: 8352612: No way to add back lint categories after "none" [v2]

[Archie Cobbs]

> This PR relates to the `-Xlint:none` flag. Currently, it not only disables all lint categories as one would expect, but it also disables all non-mandatory warnings, period. In other words, `-Xlint:none` has `-nowarn` as a hidden side-effect. So for example, trying to do `-Xlint:none,serial` to enable only the `serial` lint category is futile: the category will be enabled but the warnings won't ever appear. This PR removes that hidden side-effect, and also clarifies some of the help output.

Archie Cobbs has updated the pull request incrementally with one additional commit since the last revision:

  Update copyright.

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/24227/files
  - new: https://git.openjdk.org/jdk/pull/24227/files/8702f04f..5fb4ad30

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=24227&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=24227&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/24227.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24227/head:pull/24227

PR: https://git.openjdk.org/jdk/pull/24227