feat(MeasureTheory/LpSeminorm): add rpow_add_le_mul_rpow_add_rpow' variants

[pitmonticone]

Add two variants of ENNReal.rpow_add_le_mul_rpow_add_rpow using LpAddConst as the constant, valid for all 0 ≤ p (not just 1 ≤ p).

Upstreamed from the Carleson project.

Co-authored-by: Leo Diedering 129694072+ldiedering@users.noreply.github.com

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[github-actions]

PR summary 3dc571db33

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

+ rpow_add_le_mul_rpow_add_rpow'
+ rpow_add_le_mul_rpow_add_rpow''

You can run this locally as follows

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

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

The doc-module for scripts/pr_summary/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/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).

[fpvandoorn]

This file is not really the right place for these lemmas, but I understand that you add them here because LpAddConst is defined here.
However, since this is just about inequalities of ENNReal-powers, I think the new material and LpAddConst should be done in Mathlib.Analysis.MeanInequalitiesPow.

[themathqueen]

instead of ending the namespace and then re-opening the namespace later and reintroducing the variables, why not just do _root_.ENNReal. for the two lemmas?
Edit: never-mind, I see the comment above that this is the wrong file anyway?