RFR: 8286908: ECDSA signature should not return parameters

[Weijun Wang]

Let ECDSA's `engineGetParameters()` always return null. At the same time, remove the remembered `sigParams` field. One behavior change is that after calling `setParameter()`, one can call `init()` again with a key using different parameters. I think this should be allowed since we are reusing the signature object with a brand new key.

`setParameter` is kept unchanged to be able to deal with certificates still having parameters after the signature algorithm object identifier. See https://bugs.openjdk.java.net/browse/JDK-8225745.

Also added SHA1withECDSA to the no-NULL list in `KnownOIDs`.

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Commit messages:
 - the fix

Changes: https://git.openjdk.java.net/jdk/pull/8758/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8758&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8286908
  Stats: 96 lines in 3 files changed: 59 ins; 29 del; 8 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8758.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8758/head:pull/8758

PR: https://git.openjdk.java.net/jdk/pull/8758