RFR: 8340103: Add internal set_flag function to VMATree [v16]

[Johan Sjölen]

> Hi!
> 
> The old VirtualMemoryTracker has a method set_reserved_region_type(address, flag). We implement this for the new VMATree implementation by altering the signature slightly to set_reserved_region_type(address, size, flag). This simplifies the implementation greatly for our new data structure and leads to trivial changes for the callers (all callers already know the size).
> 
> This PR implements the internal implementation along with tests, but does not change any callers.
> 
> I also do a few cleanups:
> 
> - Change `Node` to `TreeNode` in tests, we've seen build failures because of this (probably a precompiled headers issue)
> - Add a few `print_on` methods for  easy debugging
> - Add a `size` alias, it was a bit confusing that some functions took an argument `position sz`, so changed that to `size sz` 
> 
> Thanks.

Johan Sjölen has updated the pull request incrementally with one additional commit since the last revision:

  Make a comment about this nifty trick

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Changes:
  - all: https://git.openjdk.org/jdk/pull/20994/files
  - new: https://git.openjdk.org/jdk/pull/20994/files/13518a09..5ab0d4e9

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20994&range=15
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20994&range=14-15

  Stats: 2 lines in 1 file changed: 2 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/20994.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20994/head:pull/20994

PR: https://git.openjdk.org/jdk/pull/20994