chore: reorder mvfderiv lemmas

[grunweg]

Previously, there was a section of lemmas about mvfderivWithin, then a corresponding section about mvfderiv. Ensuring these sections matched was a bit cumbersome, as one had to scroll back and forth all the time.

Instead, move a lemma mvfderiv_foo right after its counterpart mvfderivWithin_foo. (Usually, this matches how it is proved also.) This matches the structure in e.g. the file about mfderiv.

---

• depends on: chore: golf mvfderiv(Within)_zero #43986

[github-actions]

PR summary 8bf380361a

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference

---

Declarations diff (regex)

+ mvfderivWithin_zero_of_not_mdifferentiableWithinAt
+ mvfderiv_zero_of_not_mdifferentiableAt

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 8bf3803).

• +2 new declarations
• −0 removed declarations

+mvfderivWithin_zero_of_not_mdifferentiableWithinAt
+mvfderiv_zero_of_not_mdifferentiableAt

---

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

Current commit 8bf380361a
Reference commit b1007d8abf

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).

[mathlib-dependent-issues]

This PR/issue depends on:

• chore: golf mvfderiv(Within)_zero #43986
  By Dependent Issues (🤖). Happy coding!