RFR: 8273157: Add convenience methods to Messager [v3]

[Joe Darcy]

> Hello,
> 
> Please review the addition of a half dozen convenience methods to Messager to allow code like
> 
>     m.printError("Error message")
> 
> rather than
> 
>     m.printMessage(Kind.ERROR, "Error message")
> 
> For each of notes, warnings, and errors, two methods are added: one taking a message, the second taking a message and an element. There are other overloads of the printMessage method with additional arguments, but they are less commonly used and weren't judged to merit dedicated convenience methods.
> 
> The changeset also refactors ~125 of ~150 call sites of printMessage in the langtools regression tests to use the new methods. The updated tests (or tests using the updated files) all pass. I became more convinced of the utility of the new methods after using them in the refactoring.
> 
> I'll run a script to update the copyright years before any integration.
> 
> CSR for review: https://bugs.openjdk.java.net/browse/JDK-8273160

Joe Darcy has updated the pull request incrementally with one additional commit since the last revision:

  Fix imports.

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/5309/files
  - new: https://git.openjdk.java.net/jdk/pull/5309/files/af256daf..6238078f

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=5309&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=5309&range=01-02

  Stats: 65 lines in 37 files changed: 3 ins; 55 del; 7 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5309.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5309/head:pull/5309

PR: https://git.openjdk.java.net/jdk/pull/5309