refactor(Data/Finset/Sups): rename powerset_union/inter

[mo271]

... to powerset_sups/infs

Rename Finset.powerset_union to Finset.powerset_sups and Finset.powerset_inter to Finset.powerset_infs to reflect that they compute pointwise operations ⊻ and ⊼.

Add deprecation aliases.

A follow-up (#42521) will add Finset.powerset_inter back (with a different meaning).

---

[github-actions]

PR summary 791d258ca7

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference

---

Declarations diff (regex)

+ powerset_infs
+ powerset_sups

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 791d258).

• +2 new declarations
• −0 removed declarations

+Finset.powerset_infs
+Finset.powerset_sups

---

No changes to strong technical debt.

No changes to weak technical debt.

Current commit 791d258ca7
Reference commit e506e4611d

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).

[github-actions]

✅ PR Title Formatted Correctly

The title of this PR has been updated to match our commit style conventions.
Thank you!