test: cover OPML import behavior

[sgallese]

Summary

• cover top-level OPML feeds being assigned to the default group
• cover Read You OPML flags for notification, full-content, and browser behavior
• cover feed-name fallback from the feed URL domain

Test plan

• ANDROID_HOME=/Users/sgallese/Library/Android/sdk ./gradlew testGithubReleaseUnitTest --tests me.ash.reader.infrastructure.rss.OPMLDataSourceTest --max-workers=2
• ANDROID_HOME=/Users/sgallese/Library/Android/sdk ./gradlew testGithubReleaseUnitTest --max-workers=2
• ANDROID_HOME=/Users/sgallese/Library/Android/sdk ./gradlew assembleGithubRelease --max-workers=2
• ANDROID_HOME=/Users/sgallese/Library/Android/sdk gradle assembleGithubRelease --max-workers=2