feat(Topology/Separation/Hausdorff): add tendsto_nhds_unique_of_forall

[tb65536]

This PR adds the variant tendsto_nhds_unique_of_forall and switches a few occurrences of tendsto_nhds_unique to a more appropriate variant (either tendsto_nhds_unique_of_forall or tendsto_nhds_unique_of_eventuallyEq).

---

[github-actions]

PR summary 7d0ff7ddf8

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference

---

Declarations diff (regex)

+ tendsto_nhds_unique_of_forall

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 -- stale, waiting for the new build)

✅ Lean-aware diff — post-build, computed from the Lean environment (commit 88f5b8b).

• +1 new declarations
• −0 removed declarations

+tendsto_nhds_unique_of_forall

---

No changes to strong technical debt.

No changes to weak technical debt.

Current commit 7d0ff7ddf8
Reference commit d7f2dbea7d

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).

[mathlib-merge-conflicts]

This pull request has conflicts, please merge master and resolve them.