Provide simple interface to query estimated min/max liquidity

[tnull]

This PR provides a simple interface to query ProbablisticScorerUsingTime's estimate of a channels mininum/maximum liquidity.

[codecov-commenter]

Codecov Report

Merging #1549 (13fa186) into main (abf6564) will decrease coverage by 0.01%.
The diff coverage is n/a.

❗ Current head 13fa186 differs from pull request most recent head 717365f. Consider uploading reports for the commit 717365f to get more accurate results

@@            Coverage Diff             @@
##             main    #1549      +/-   ##
==========================================
- Coverage   90.96%   90.94%   -0.02%     
==========================================
  Files          80       80              
  Lines       43610    43610              
  Branches    43610    43610              
==========================================
- Hits        39670    39663       -7     
- Misses       3940     3947       +7     

Impacted Files	Coverage Δ
lightning/src/routing/scoring.rs	97.08% <ø> (ø)
lightning/src/chain/onchaintx.rs	93.98% <0.00%> (-0.93%)	⬇️
lightning/src/ln/functional_tests.rs	96.98% <0.00%> (-0.08%)	⬇️
lightning-net-tokio/src/lib.rs	77.77% <0.00%> (+0.61%)	⬆️

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