Add unit test report generator (#7411)

Currently not called by any gradle plugins or workflows.
Generates a root level file called `test-report.md` with info for a
configurable number of commits using the GitHub API. Can be called
locally for testing with a tiny `main` function configuring an api token
and commit count.

<details>
<summary>Example output</summary>

### Unit Tests

*All tests passing*

### Instrumentation Tests

| | [#7344](#7344)
| [#7404](#7404) |
[#7412](#7412) |
[#7409](#7409) |
[#7365](#7365) |
Success Rate |
| :--- | :---: | :---: | :---: | :---: | :---: | :--- |
| firebase-database |
[✅](https://github.com/firebase/firebase-android-sdk/actions/runs/18049430908/job/51368583464)
|
[⛔](https://github.com/firebase/firebase-android-sdk/actions/runs/18022175955/job/51281984677)
| | |
[⛔](https://github.com/firebase/firebase-android-sdk/actions/runs/17951371470/job/51051886073)
| ⛔ 33% |
| firebase-common |
[✅](https://github.com/firebase/firebase-android-sdk/actions/runs/18049430908/job/51368583401)
|
[⛔](https://github.com/firebase/firebase-android-sdk/actions/runs/18022175955/job/51281984633)
| | |
[✅](https://github.com/firebase/firebase-android-sdk/actions/runs/17951371470/job/51051886001)
| ⛔ 66% |
| firebase-config:bandwagoner |
[✅](https://github.com/firebase/firebase-android-sdk/actions/runs/18049430908/job/51368583437)
|
[✅](https://github.com/firebase/firebase-android-sdk/actions/runs/18022175955/job/51281984627)
| | |
[⛔](https://github.com/firebase/firebase-android-sdk/actions/runs/17951371470/job/51051886027)
| ⛔ 66% |
| firebase-functions |
[✅](https://github.com/firebase/firebase-android-sdk/actions/runs/18049430908/job/51368583469)
|
[✅](https://github.com/firebase/firebase-android-sdk/actions/runs/18022175955/job/51281984675)
| | |
[⛔](https://github.com/firebase/firebase-android-sdk/actions/runs/17951371470/job/51051886083)
| ⛔ 66% |
| firebase-inappmessaging |
[✅](https://github.com/firebase/firebase-android-sdk/actions/runs/18049430908/job/51368583442)
|
[✅](https://github.com/firebase/firebase-android-sdk/actions/runs/18022175955/job/51281984686)
| | |
[⛔](https://github.com/firebase/firebase-android-sdk/actions/runs/17951371470/job/51051886106)
| ⛔ 66% |

*+58 passing SDKs*


</details>

Author: emilypgoogle

plugins/src/main/java/com/google/firebase/gradle/plugins/report/ReportCommit.kt

@@ -0,0 +1,23 @@
+/*
+ * Copyright 2025 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.google.firebase.gradle.plugins.report
+
+/**
+ * @param sha Commit SHA.
+ * @param pr GitHub PR number that was squashed to create this commit. Used only for display
+ *   purposes, does not affect logic.
+ */
+data class ReportCommit(val sha: String, val pr: Int)

plugins/src/main/java/com/google/firebase/gradle/plugins/report/TestReport.kt

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2025 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.google.firebase.gradle.plugins.report
+
+/**
+ * Represents a single run of a test in CI. One unit/instrumentation test workflow run creates many
+ * `TestReport`s, one for each tested SDK.
+ *
+ * @param name SDK name of the associated test run.
+ * @param type What type of test result this is, either unit or instrumentation test.
+ * @param status Conclusion status of the test run, `SUCCESS`/`FAILURE` for typical results, `OTHER`
+ *   for ongoing runs and unexpected data.
+ * @param commit Commit SHA this test was run on.
+ * @param url Link to the GHA test run info, including logs.
+ */
+data class TestReport(
+  val name: String,
+  val type: Type,
+  val status: Status,
+  val commit: String,
+  val url: String,
+) {
+  enum class Type {
+    UNIT_TEST,
+    INSTRUMENTATION_TEST,
+  }
+
+  enum class Status {
+    SUCCESS,
+    FAILURE,
+    OTHER,
+  }
+}