feat(Analysis/PSeries): add version of Cauchy condensation with weaker assumptions

[jvanwinden]

Add a version of summable_condensed_iff_of_nonneg which only requires that f is eventually positive and antitone.

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[github-actions]

PR summary fe7afa6e1a

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

+ summable_condensed_iff_of_nonneg'

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).

[jvanwinden]

This came up when trying to prove non-summability of fun n ↦ 1 / (n * (Real.log n).sqrt) and was discussed here. Some things to consider:

• What is the 'canonical' way of encoding eventual monotonicity along a filter? (i.e., should h_mono be rewritten)
• Would it be good to also have a version of summable_condensed_iff with eventual antitonicity?