feat(Combinatorics/SimpleGraph/Decomp): dropUntil API to match existing takeUntil API

[SnirBroshi]

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Slightly more complicated theorems than usual "API" though.

[github-actions]

PR summary 5488ebe5f0

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference

---

Declarations diff (regex)

+ dropUntil_append_of_mem_left
+ dropUntil_append_of_notMem_left
+ dropUntil_dropUntil
+ mem_support_takeUntil_of_mem_support_dropUntil
+ notMem_dropLast_support_takeUntil_iff_mem_support_takeUntil
+ notMem_dropLast_support_takeUntil_of_mem_support_takeUntil
+ takeUntil_append_of_notMem_left

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 5488ebe).

• +7 new declarations
• −0 removed declarations

+SimpleGraph.Walk.dropUntil_append_of_mem_left
+SimpleGraph.Walk.dropUntil_append_of_notMem_left
+SimpleGraph.Walk.dropUntil_dropUntil
+SimpleGraph.Walk.mem_support_takeUntil_of_mem_support_dropUntil
+SimpleGraph.Walk.notMem_dropLast_support_takeUntil_iff_mem_support_takeUntil
+SimpleGraph.Walk.notMem_dropLast_support_takeUntil_of_mem_support_takeUntil
+SimpleGraph.Walk.takeUntil_append_of_notMem_left

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No changes to strong technical debt.

No changes to weak technical debt.

Current commit 5488ebe5f0
Reference commit f34e762642

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).