Do not report detekt LargeClass issues on test classes (#7713)

detekt's default configuration excludes test source sets from
`TooManyFunctions` and `StringLiteralDuplication`, but not from
`LargeClass`, so large test classes were reported and had to carry a
`@Suppress("LargeClass")` annotation.

Add the same kind of exclusion to the `LargeClass` rule in
`tools/detekt/detekt.yml` and remove the 24 now-redundant suppressions
from test files. The two remaining suppressions are in production code,
where the rule still applies.

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

libraries/mediaviewer/impl/src/test/kotlin/io/element/android/libraries/mediaviewer/impl/datasource/EventItemFactoryTest.kt

@@ -62,7 +62,6 @@ import kotlinx.collections.immutable.toImmutableList
 import org.junit.Test
 import kotlin.time.Duration.Companion.seconds
 
-@Suppress("LargeClass")
 class EventItemFactoryTest {
     @Test
     fun `create check all null cases`() {

libraries/mediaviewer/impl/src/test/kotlin/io/element/android/libraries/mediaviewer/impl/viewer/MediaViewerPresenterTest.kt

@@ -64,7 +64,6 @@ private val TESTED_MEDIA_INFO = anApkMediaInfo(
     senderId = A_USER_ID,
 )
 
-@Suppress("LargeClass")
 class MediaViewerPresenterTest {
     @get:Rule
     val warmUpRule = WarmUpRule()