RFR: 8241306: Add SignatureMethodParameterSpec subclass for RSASSA-PSS params

[Weijun Wang]

This enhancement contains the following code changes:

1. Create a new public API `javax/xml/crypto/dsig/spec/RSAPSSParameterSpec` and remove the internal one.
2. Update marshaling and unmarshaling code inside `DOMRSAPSSSignatureMethod` so it understands extra fields in `PSSParameterSpec` and is aware of the defaults in both directions.
3. Update `DOMSignedInfo` so that secure validation can restrict `DigestMethod` used inside `RSAPSSParameterSpec`
4. Tests

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Commit messages:
 - 8241306: Add SignatureMethodParameterSpec subclass for RSASSA-PSS params

Changes: https://git.openjdk.java.net/jdk/pull/3181/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3181&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8241306
  Stats: 1310 lines in 11 files changed: 1159 ins; 105 del; 46 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3181.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3181/head:pull/3181

PR: https://git.openjdk.java.net/jdk/pull/3181