feat(MeasureTheory): coercion of a finite sum of scalar multiples in Lp

[FrankieNC]

Adds Lp.coeFn_finsetSum_smul: for a finite set s, scalars c : ι → 𝕜, and a family f : ι → Lp E p μ, the coercion of ∑ i ∈ s, c i • f i is almost everywhere equal to ∑ i ∈ s, c i • ⇑(f i).

This is the finite-sum, scalar-multiple companion to Lp.coeFn_smul and Lp.coeFn_finsetSum.

[github-actions]

PR summary 3a046c2025

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 (regex)

+ coeFn_finsetSum_smul

You can run this locally as follows

## from your `mathlib4` directory:
git clone https://github.com/leanprover-community/mathlib-ci.git ../mathlib-ci

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

## more verbose report:
../mathlib-ci/scripts/pr_summary/declarations_diff.sh long <optional_commit>

The doc-module for scripts/pr_summary/declarations_diff.sh in the mathlib-ci repository contains some details about this script.

Declarations diff (Lean)

✅ Lean-aware diff — post-build, computed from the Lean environment (commit 3a046c2).

• +1 new declarations
• −0 removed declarations

+MeasureTheory.Lp.coeFn_finsetSum_smul

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No changes to strong technical debt.

No changes to weak technical debt.

Current commit 3a046c2025
Reference commit 005f0aa67b

This script lives in the mathlib-ci repository. To run it locally, from your mathlib4 directory:

git clone https://github.com/leanprover-community/mathlib-ci.git ../mathlib-ci
../mathlib-ci/scripts/reporting/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).