RFR: 8354433: Assert in AbstractRBTree::visit_range_in_order(const K& from, const K& to, F f) is wrong

[Casper Norrbin]

There was an assert in `AbstractRBTree::visit_range_in_order` that could incorrectly trigger when:
- The range contains no nodes, **but**
- Nodes exist **outside** that range.

The assert checked `from <= to` indirectly via `from <= start <= to`, but `start` could be valid outside that range.

To fix this, I added the ability to supply a direct key comparison for intrusive trees to the `COMPARATOR` template. This already existed in the non-intrusive RBTree, and works the same as the other extra `cmp` function.

Additionally, I found another wrong assert in `replace_at_cursor` that is also fixed here.

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Commit messages:
 - assert fix with key comparator for intrusive trees

Changes: https://git.openjdk.org/jdk/pull/24658/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24658&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8354433
  Stats: 93 lines in 3 files changed: 55 ins; 18 del; 20 mod
  Patch: https://git.openjdk.org/jdk/pull/24658.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24658/head:pull/24658

PR: https://git.openjdk.org/jdk/pull/24658