feat(Topology): add bounded variation precomposition lemmas

[CoolRmal]

This PR adds precomposition lemmas for bounded variation on linearly ordered domains.

It records the global monotone/antitone eVariationOn inequalities, then uses them to show that BoundedVariationOn and LocallyBoundedVariationOn are stable under precomposition by monotone or antitone maps, both for On hypotheses and global monotone/antitone functions.

Created with the help of codex.

[github-actions]

PR summary 5bedac458a

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference

---

Declarations diff (regex)

+ _root_.BoundedVariationOn.comp_antitone
+ _root_.BoundedVariationOn.comp_antitoneOn
+ _root_.BoundedVariationOn.comp_monotone
+ _root_.BoundedVariationOn.comp_monotoneOn
+ _root_.LocallyBoundedVariationOn.comp_antitone
+ _root_.LocallyBoundedVariationOn.comp_antitoneOn
+ _root_.LocallyBoundedVariationOn.comp_monotone
+ _root_.LocallyBoundedVariationOn.comp_monotoneOn
+ comp_le_of_antitone
+ comp_le_of_monotone

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 5bedac4).

• +10 new declarations
• −0 removed declarations

+BoundedVariationOn.comp_antitone
+BoundedVariationOn.comp_antitoneOn
+BoundedVariationOn.comp_monotone
+BoundedVariationOn.comp_monotoneOn
+LocallyBoundedVariationOn.comp_antitone
+LocallyBoundedVariationOn.comp_antitoneOn
+LocallyBoundedVariationOn.comp_monotone
+LocallyBoundedVariationOn.comp_monotoneOn
+eVariationOn.comp_le_of_antitone
+eVariationOn.comp_le_of_monotone

---

No changes to strong technical debt.

No changes to weak technical debt.

Current commit 5bedac458a
Reference commit 69b866d83a

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).