RFR: 8358099: PEM spec updates [v3]

[Anthony Scarpino]

> Hi, I need a review of some PEM updates.  `PEMRecord.pem` is renamed to `content` to better describe that it is the base64 content and not including the header and footer. Additionally, `PEMRecord.getEncoded()` is removed and some javadoc clarifications for PEMEncoder and PEMDecoder.  Thanks.

Anthony Scarpino has updated the pull request incrementally with one additional commit since the last revision:

  wrong "PEM types"

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Changes:
  - all: https://git.openjdk.org/jdk/pull/25620/files
  - new: https://git.openjdk.org/jdk/pull/25620/files/cbb00924..afdc32e5

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=25620&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=25620&range=01-02

  Stats: 3 lines in 1 file changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/25620.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25620/head:pull/25620

PR: https://git.openjdk.org/jdk/pull/25620