Fix RetrievalPrecisionRecallCurve axis labels and swap axis

[carandraug]

What does this PR do?

Fixes #3403 .

Somehow, the plots for retrieval precision recall curves evolved to label the axis True and False positive rates (TPR and FPR). These are the same labels used in ROCs. There are three isues: the label FPR is wrong (precision and FPR are not the same thing), it is weird to use TPR (TPR and Recall are the same) as label name if the other label name is Precision, it is odd to use Precision on the x axis. This PR addresses the three things (the first two issues in the first commit), the third issue in the second commit).

I think the reason we ended up in this situation is (repeated here from the commit messages in this PR):

It seems this issue was originally introduced as part of #1623 when
the plot method was first added using plot_binary_roc_curve. ROCs do
plot TPR against FPR. I'm guessing that when plot_binary_roc_curve
was replaced with plot_curve in #1660, those wrong labels were kept.

and

It is standard to use Recall on the x axis and Precision on the y axis
but the current implementation has it flipped. This is possibly
because the implementation evolved (incorrectly) from ROCs where TPR
(aka Recall) is on the y axis and FPR on the x axis.

Before submitting

• Was this discussed/agreed via a Github issue? (no need for typos and docs improvements)
• Did you read the contributor guideline, Pull Request section? yes
• Did you make sure to update the docs? There are no associated docs.
• Did you write any new necessary tests? There are no associated tests.

PR review

Anyone in the community is free to review the PR once the tests have passed.
If we didn't discuss your PR in Github issues there's a high chance it will not be merged.

[Copilot]

Pull request overview

This PR fixes the RetrievalPrecisionRecallCurve.plot() visualization to correctly present a precision–recall curve, aligning both axis labels and axis orientation with standard PR-curve conventions and with TorchMetrics’ classification PR-curve plotting.

Changes:

• Swap plotted axes so Recall is on the x-axis and Precision is on the y-axis.
• Correct axis labels from ROC terminology (FPR/TPR) to PR terminology (Recall/Precision).

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Codecov Report

❌ Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 31%. Comparing base (d184220) to head (08dcc13).
⚠️ Report is 7 commits behind head on master.
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HEAD has 792 uploads less than BASE

Flag	BASE (d184220)	HEAD (08dcc13)
torch2.0.1+cpu	20	2
python3.10	129	12
Windows	30	3
cpu	218	20
torch2.9.1	9	0
macOS	39	3
python3.12	89	8
torch2.9.1+cpu	30	3
torch2.8.0+cpu	30	3
torch2.8.0	10	1
Linux	149	14
torch2.10.0	10	1
torch2.7.1+cpu	20	2
torch2.10.0+cpu	20	2
torch2.4.1+cpu	10	0
torch2.2.2+cpu	10	1
torch2.1.2+cpu	10	1
torch2.5.1+cpu	10	1
torch2.0.1	10	1
torch2.3.1+cpu	9	1
torch2.6.0+cpu	10	1

Additional details and impacted files

@@           Coverage Diff            @@
##           master   #3404     +/-   ##
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- Coverage      37%     31%     -6%     
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  Files         349     349             
  Lines       19901   19906      +5     
========================================
- Hits         7264    6169   -1095     
- Misses      12637   13737   +1100     

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