docs: add issue template for point-release

This is the issue format I've been using for e.g. v0.80.3 (#4829),
so I'm adding to the repo, to make it easier to find and reuse.
In the process, I'm cleaning out the old "release testnet" checklist,
because that's not a process we follow regularly anymore: we don't have
regular or frequent chain resets.

.github/ISSUE_TEMPLATE/point_release.md

@@ -0,0 +1,30 @@
+---
+name: Point release
+about: Checklist for preparing a point release for tooling
+title: Release vX.Y.Z, via point-release
+labels: ''
+assignees: ''
+---
+
+# Tooling Release
+
+<!--
+Explain the rationale for this release: did a particular bugfix land that we want to ship quickly?
+Is an external consumer blocked on a new RPC?
+-->
+In order to ship some minor improvements and bug fixes, let's prepare a `vX.Y.Z.` release, flushing out the current contents of the main branch.
+
+## Changes to include
+<!--
+Explain the rationale for this release: did a particular bugfix land that we want to ship quickly?
+Is an external consumer blocked on a new RPC?
+-->
+
+- [ ] Everything on current main
+- [ ] Feature foo in PR: 
+- [ ] Feature bar in PR: 
+
+## Compatibility
+As this is a point-release, all changes must be fully compatible for all nodes and clients.
+Careful attention should be given to the delta between most recent tag on the main branch:
+https://github.com/penumbra-zone/penumbra/compare/v(X.Y.(Z-1)..main