Add messages for config changes (#3803)

* Automatically label Wasmtime `Config` object changes

* Add the "Label Messager" github action

This allows us to have custom messages left in comments on issues and pull
requests when they get labeled with a specific label.

* Add a message for `wasmtime:config`-labeled pull requests

* CI: Consolidate issue/PR triage workflows

.github/label-messager/wasmtime-config.md

@@ -0,0 +1,51 @@
+It looks like you are changing Wasmtime's configuration options. Make sure to
+complete this check list:
+
+* [ ] If you added a new `Config` method, you wrote extensive documentation for
+      it.
+
+  <details>
+
+  Our documentation should be of the following form:
+
+  ```text
+  Short, simple summary sentence.
+
+  More details. These details can be multiple paragraphs. There should be
+  information about not just the method, but its parameters and results as
+  well.
+
+  Is this method fallible? If so, when can it return an error?
+
+  Can this method panic? If so, when does it panic?
+
+  # Example
+
+  Optional example here.
+  ```
+
+  </details>
+
+* [ ] If you added a new `Config` method, or modified an existing one, you
+  ensured that this configuration is exercised by the fuzz targets.
+
+  <details>
+
+  For example, if you expose a new strategy for allocating the next instance
+  slot inside the pooling allocator, you should ensure that at least one of our
+  fuzz targets exercises that new strategy.
+
+  Often, all that is required of you is to ensure that there is a knob for this
+  configuration option in [`wasmtime_fuzzing::Config`][fuzzing-config] (or one
+  of its nested `struct`s).
+
+  Rarely, this may require authoring a new fuzz target to specifically test this
+  configuration. See [our docs on fuzzing][fuzzing-docs] for more details.
+
+  </details>
+
+* [ ] If you are enabling a configuration option by default, make sure that it
+  has been fuzzed for at least two weeks before turning it on by default.
+
+[fuzzing-config]: https://github.com/bytecodealliance/wasmtime/blob/ca0e8d0a1d8cefc0496dba2f77a670571d8fdcab/crates/fuzzing/src/generators.rs#L182-L194
+[fuzzing-docs]: https://docs.wasmtime.dev/contributing-fuzzing.html