Add typing information for use by typesafegithub (#814)

Introduces type descriptor YAML files for GitHub
Actions in the repository, improving type safety and documentation for
action inputs and outputs. It also adds a new GitHub Actions workflow to
validate these typings automatically on pushes and pull requests. The
changes are grouped into the addition of type descriptor files for
various actions and the automation of their validation.

https://github.com/typesafegithub/github-actions-typing

**Type descriptor files for GitHub Actions:**

* Added `action-types.yml` files to `setup-gradle`,
`dependency-submission`, and `wrapper-validation` actions, specifying
input and output types for each action to improve type safety and
documentation.
[[1]](diffhunk://#diff-542de74831b6dc1954ff20a4c329b170053c82087ea7df742bd536156133f25bR1-R171)
[[2]](diffhunk://#diff-44708a3af3d0f3cfed1873f9b77d7e815c6c14e941fa3dd5ed08835a69d67855R1-R146)
[[3]](diffhunk://#diff-3fe1028d7aa5ee815c90fa580d4f62e646f0b9a4b7372f227fc131a56948ace0R1-R17)

**Automation and validation:**

* Introduced a new GitHub Actions workflow
`.github/workflows/ci-validate-typings.yml` to automatically validate
action typings on pushes to `main` and `release/**` branches, as well as
on pull requests. This uses the `github-actions-typing` action for
validation.

wrapper-validation/action-types.yml

@@ -0,0 +1,17 @@
+# Type descriptors based on https://github.com/typesafegithub/github-actions-typing
+inputs:
+  min-wrapper-count:
+    type: integer
+
+  allow-snapshots:
+    type: boolean
+
+  allow-checksums:
+    type: list
+    separator: ','
+    list-item:
+      type: string
+
+outputs:
+  failed-wrapper:
+    type: string