<i18n dev> RFR: JDK-8325908: Finish removal of IntlTest and CollatorTest [v2]

[Justin Lu]

> Please review this PR which fixes / finishes the rest of the IntlTest test framework removal in java.text and java.util.i18n tests.
> 
> For context, the IntlTest class only ran methods prefixed by _test_ or _Test_ with public visibility and was originally removed due to some tests spuriously passing that were not aware of the specific running requirements.
> 
> This PR includes the following changes,
> - There were some tests with package-private visibility that were never ran by IntlTest. Those tests do appear to be valid tests, and thus have been updated with `@Test` annotation.
> - The test method DFSExponenTest() in DFSExponential.java was not prefixed by test and thus never ran by IntlTest. It is a valid test and should be ran as well.
> - DateFormatRoundTripTest.java was supposed to remain a non JUnit test, however the run invocation was converted to `@run junit ...` this has been switched back to `@run main ...`
> - There were two instances of the script missing some tests that should have had their methods updated with the `@Test` annotation: APITest.java and DFSSerialization.java. These tests have been updated accordingly.

Justin Lu has updated the pull request incrementally with one additional commit since the last revision:

  improve method name as suggested, remove unusued clutter

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/17858/files
  - new: https://git.openjdk.org/jdk/pull/17858/files/c04309a7..35f06d62

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=17858&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=17858&range=00-01

  Stats: 17 lines in 1 file changed: 0 ins; 9 del; 8 mod
  Patch: https://git.openjdk.org/jdk/pull/17858.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17858/head:pull/17858

PR: https://git.openjdk.org/jdk/pull/17858