RFR: 8320575: generic type information lost on mandated parameters of record's compact constructors [v18]

[Vicente Romero]

> Reflection is not retrieving generic type information for mandated parameters. This is a known issue which has been explicitly stated in the API of some reflection methods. Fix for [JDK-8292275](https://bugs.openjdk.org/browse/JDK-8292275) made the parameters of compact constructors of record classes `mandated` as specified in the spec. But this implied that users that previous to this change could retrieve the generic type of parameters of compact constructors now they can't anymore. The proposed fix is to try to retrieve generic type information for mandated parameters if available plus changing the spec of the related reflection methods.
> 
> TIA

Vicente Romero has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 18 additional commits since the last revision:

 - Merge branch 'master' into JDK-8320575
 - code refactoring
 - additional tests
 - special case the new code for records only
 - adding more tests
 - Update test/jdk/java/lang/reflect/records/RecordReflectionTest.java
   
   Co-authored-by: Andrey Turbanov <turbanoff at gmail.com>
 - making the javadoc less general
 - Merge branch 'master' into JDK-8320575
 - adding comment to jcod file
 - adding a comment to the test
 - ... and 8 more: https://git.openjdk.org/jdk/compare/24a987e7...0237d72c

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/17070/files
  - new: https://git.openjdk.org/jdk/pull/17070/files/775599cc..0237d72c

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=17070&range=17
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=17070&range=16-17

  Stats: 24018 lines in 1560 files changed: 8871 ins; 10734 del; 4413 mod
  Patch: https://git.openjdk.org/jdk/pull/17070.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17070/head:pull/17070

PR: https://git.openjdk.org/jdk/pull/17070