feat: simplify computations in complex analysis by extracting frequently-used lemmas

[kebekus]

Simplify several computations in complex analysis by extracting lemmas that are used more than once. At present, the gain is real but modest. It will become more visible as more computations are added.

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[github-actions]

PR summary cea67ce127

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)

+ mul_abs_sin_le_norm_circleMap_zero_sub
+ norm_circleMap_zero_sub_sq
+ norm_circleMap_zero_sub_sq'

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 cea67ce).

• +3 new declarations
• −0 removed declarations

+mul_abs_sin_le_norm_circleMap_zero_sub
+norm_circleMap_zero_sub_sq
+norm_circleMap_zero_sub_sq'

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No changes to strong technical debt.
No changes to weak technical debt.

Current commit cea67ce127
Reference commit dec5b2b780

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.py 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).