RFR: 8297065: DerOutputStream operations should not throw IOExceptions [v4]

[Weijun Wang]

> This is mostly cleanup. Everything around `DerOutputStream` no longer throws an `IOException`. This includes:
> 
> - Remove unnecessary `throws IOException` in code and spec
> - Remove `catch (IOException ioe)` blocks. If new exception is thrown, remove further `throws` in code and spec
> - More classes implementing `DerEncoder` if they have a `encode(DerOutputStream)` method
> - Modify `write(bytes)` to `writeBytes(bytes)` to avoid IOE
> - Some unused methods removed
> - `DerOutputStream` is final
> 
> The only actual changes (still trivial) are:
> - Since `PKCS7::encodeSignedData(OutputStream out)` is removed, its usages in `PKCS7::constructToken` and `TsaSigner::createResponse` (in test) are modified to use another method with a `DerOutputStream` argument.
> - In PKCS8Key, since `getEncodedInternal` never returns non-null, remove null check on result
> - Since `DerOutputStream` is final, no need to clone bytes in `encode` of `X509CertImpl` and `X509CRLImpl`.

Weijun Wang has updated the pull request incrementally with one additional commit since the last revision:

  one extra removal

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/11302/files
  - new: https://git.openjdk.org/jdk/pull/11302/files/3c70371b..f18a6786

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=11302&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=11302&range=02-03

  Stats: 8 lines in 1 file changed: 0 ins; 8 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/11302.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11302/head:pull/11302

PR: https://git.openjdk.org/jdk/pull/11302