feat: norm_num extension for Real.sqrt and NNReal.sqrt

[dupuisf]

This PR introduces a norm_num extension for both Real.sqrt and NNReal.sqrt. While the version for Real.sqrt can handle both integers and rationals, the version for NNReal.sqrt can only deal with integers, due to a limitation of norm_num (i.e. the IsRat type requires a Ring instance).

I put the extension directly in Data/Real/Sqrt, but I could put them in a separate file in Tactic/NormNum if this is deemed better. (The obvious downside is that potential users would need to import the file explicitly.)

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[github-actions]

PR summary 9c84c42927

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference

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Declarations diff

+ evalNNRealSqrt
+ evalRealSqrt
+ isNat_nnrealSqrt
+ isNat_realSqrt
+ isNat_realSqrt_neg
+ isNat_realSqrt_neg_of_isRat
+ isRat_realSqrt

You can run this locally as follows

## summary with just the declaration names:
./scripts/declarations_diff.sh <optional_commit>

## more verbose report:
./scripts/declarations_diff.sh long <optional_commit>

The doc-module for script/declarations_diff.sh contains some details about this script.

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No changes to technical debt.

You can run this locally as

./scripts/technical-debt-metrics.sh pr_summary

• The relative value is the weighted sum of the differences with weight given by the inverse of the current value of the statistic.
• The absolute value is the relative value divided by the total sum of the inverses of the current values (i.e. the weighted average of the differences).

[eric-wieser]

due to a limitation of norm_num (i.e. the IsRat type requires a Ring instance).

#9915 is a rotting attempt to fix this.