RFR: 8345655: Move reservation code out of ReservedSpace [v3]

[Stefan Karlsson]

> The ReservedSpace class and its friends has a dual functionality of describing a reserved memory region AND it also reserves memory. I would like to split this so that the ReservedSpace classes only acts as data carrier about reserved memory and then have a more explicit API for reserving memory and baking a ReservedSpace given the outcome of the reservation.
> 
> See the first comment for the full description:

Stefan Karlsson has updated the pull request incrementally with one additional commit since the last revision:

  Copyright

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Changes:
  - all: https://git.openjdk.org/jdk/pull/22712/files
  - new: https://git.openjdk.org/jdk/pull/22712/files/7b053084..c936bd44

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=22712&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=22712&range=01-02

  Stats: 6 lines in 6 files changed: 0 ins; 0 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/22712.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22712/head:pull/22712

PR: https://git.openjdk.org/jdk/pull/22712