Expose inner ProbabilisticScorer accessors on CombinedScorer

[randomlogin]

This PR adds public accessors to CombinedScorer for its inner ProbabilisticScorers.

Placed in a new impl block without the G: Clone / L: Clone bounds required by new / merge / set_scores, matching the bounds on the other &self impls.

Motivation: while working on adding a probing service to ldk-node (lightningdevkit/ldk-node#815), I realized that it is useful to have scorer's internal liquidity estimates to evaluate the performance of a particular probing strategy.

Right now it is done via an ugly workaround of serializing and de-serializing the scorer to reach estimated_channel_liquidity_range and this PR aims to fix that.

It will be used in for further development of probing service, in strategy efficiency ranking.

[ldk-reviews-bot]

I've assigned @valentinewallace as a reviewer!
I'll wait for their review and will help manage the review process.
Once they submit their review, I'll check if a second reviewer would be helpful.

[ldk-claude-review-bot]

No trait method conflicts. The diff is small and straightforward — two read-only accessors returning shared references to private fields. Let me verify the doc link targets are correct (the referenced methods merge and set_scores exist on Self).

The Self::merge is at line 1850 and Self::set_scores is at line 1869 — both are on CombinedScorer, so the doc links are valid (Rust resolves Self links across impl blocks of the same type).

No issues found.

No issues found. This is a clean, minimal PR that adds two read-only accessor methods (scorer() and local_only_scorer()) to CombinedScorer, returning shared references to its private ProbabilisticScorer fields. The trait bounds correctly match other &self impl blocks, there are no naming conflicts with trait methods, and the doc-comment cross-references to Self::merge and Self::set_scores are valid.

[tnull]

Makes sense, thanks!

[tnull]

Ah, one comment post-merge: for the next time, please provide a better commit message, explaining the motivation and nature of the change. Please refer to https://cbea.ms/git-commit/ for guidance.