feat(MeasureTheory): add formulas for the measures formed by a density with respect to counting or dirac measures.

[DavidLedvinka]

Like with most theorems that ultimately rely on application of dirac measures, there are primed versions for when the function (or set in other cases) is measurable, and unprimed versions for when MeasurableSingletonClass is assumed.

[github-actions]

PR summary 1723eba85e

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

+ count_withDensity
+ count_withDensity'
+ dirac_withDensity
+ dirac_withDensity'

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).