RFR: 8243585: AlgorithmChecker::check throws confusing exception when it rejects the signer key [v4]

[Sean Mullan]

> This fix improves the exception message to better indicate when the key (and not the signature algorithm) is restricted. This change also includes a few other improvements:
> 
> - The constraints checking in `AlgorithmChecker.check()` has been improved. If the `AlgorithmConstraints` are an instance of `DisabledAlgorithmConstraints`, the internal `permits` methods are always called; otherwise the public `permits` methods are called. This makes the code easier to understand, and fixes at least one case where duplicate checks were being done.
> 
> - The above change caused some of the exception messages to be slightly different, so some tests that checked the error messages had to be updated to reflect that.
> 
> - AlgorithmDecomposer now stores the decomposed SHA algorithm names in a Map, which fixed a bug where "RSASSA-PSS" was not being restricted properly.

Sean Mullan has updated the pull request incrementally with one additional commit since the last revision:

  Address Max' comments.

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/5928/files
  - new: https://git.openjdk.java.net/jdk/pull/5928/files/f2031126..052c28f5

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=5928&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=5928&range=02-03

  Stats: 44 lines in 1 file changed: 4 ins; 16 del; 24 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5928.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5928/head:pull/5928

PR: https://git.openjdk.java.net/jdk/pull/5928