RFR: 8292225: Rename ArchiveBuilder APIs related to source and buffered addresses

[Ioi Lam]

This is a clean up of the source code to make it more readable. 
- When creating a CDS archive, we first load Java classes and create metadata objects as usual. These are call "source" objects.
- We then copy the source objects into the output buffer at their "buffered addresses".

However, we used a mix of other words to refer to them:

- The word "orig" was also used for the former.
- The words "dumped" and "relocated" were also used for the latter.

This PR renamed the names of functions and parameters to consistently use "source" and "buffered" only. In one case I reordered two fields in a class. There's otherwise no change in the code.

Please see new comments in archiveBuilder.hpp that explains the three types of addresses: "source" vs "buffered" vs "requested".

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Commit messages:
 - 8292225: Rename ArchiveBuilder APIs related to source and buffered addresses

Changes: https://git.openjdk.org/jdk/pull/10212/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10212&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8292225
  Stats: 115 lines in 8 files changed: 28 ins; 11 del; 76 mod
  Patch: https://git.openjdk.org/jdk/pull/10212.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10212/head:pull/10212

PR: https://git.openjdk.org/jdk/pull/10212