Add LoadResult.Invalid support for Paging2

This change adds LoadResult.Invalid support for Paging2 leveraging
PagingSource, such as LivePagedList and RxPagedList.

In the event of a PagingSource returning LoadResult.Invalid to its
PagedList, paging will detach the PagedList to stop attempts to load
on this PagedList and invalidate the PagingSource.

If no initial page is provided to PagedList.Builder and the initial
load fails with a LoadResult.Invalid, an IllegalStateException
will be thrown. To use a PagingSource that supports invalidation, use a
PagedList builder that accepts a factory method for PagingSource or
DataSource.Factory such as LivePagedList.

Bug: 192013267
Test: ./gradlew :paging:paging-common:test
Test: ./gradlew :paging:paging-runtime:cC
Test: ./gradlew :paging:paging-rxjava2:test
Test: ./gradlew :paging:paging-rxjava3:test
Change-Id: I97de7e67cc5fe01b2c5c5a8e13bd1926c5ca2cde

paging/rxjava3/build.gradle

diff --git a/paging/rxjava3/build.gradle b/paging/rxjava3/build.gradle
index 5b5bf91..5755ccd 100644
--- a/paging/rxjava3/build.gradle
+++ b/paging/rxjava3/build.gradle
@@ -33,9 +33,11 @@
 
     testImplementation(project(":internal-testutils-common"))
     testImplementation(project(":internal-testutils-paging"))
+    testImplementation(project(":internal-testutils-ktx"))
     testImplementation(libs.junit)
     testImplementation(libs.kotlinTest)
     testImplementation(libs.kotlinCoroutinesTest)
+    testImplementation(libs.truth)
 
     androidTestImplementation(libs.testExtJunit)
     androidTestImplementation(libs.testCore)