Report recovered files as recovered from snapshot for fully mounted searchable snapshots (elastic#92976)

Files recovered for fully mounted searchable snapshots indices are 
reported in the same manner as files recover from disk for regular 
indices. This can be confusing for users because we later introduced 
a recovered_from_snapshot_in_bytes (for snapshot based peer 
recoveries, that is not applicable to searchable snapshots indices) 
and this field is always 0 for searchable snapshots indices.

This commit changes the Recovery file details so that 
recovered_from_snapshot_in_bytes is now populated for files 
recovered for fully mounted searchable snapshots indices, which 
I think makes more sense now we have this 
recovered_from_snapshot_in_bytes field.

Author: tlrx

docs/changelog/92976.yaml

@@ -0,0 +1,6 @@
+pr: 92976
+summary: Report recovered files as recovered from snapshot for fully mounted searchable
+  snapshots
+area: Recovery
+type: bug
+issues: []

x-pack/plugin/searchable-snapshots/src/internalClusterTest/java/org/elasticsearch/xpack/searchablesnapshots/recovery/SearchableSnapshotRecoveryStateIntegrationTests.java

@@ -105,6 +105,8 @@ public void testRecoveryStateRecoveredBytesMatchPhysicalCacheState() throws Exce
 
         assertThat("Physical cache size doesn't match with recovery state data", physicalCacheSize, equalTo(recoveredBytes));
         assertThat("Expected to recover 100% of files", recoveryState.getIndex().recoveredBytesPercent(), equalTo(100.0f));
+        assertThat(recoveryState.getIndex().recoveredFromSnapshotBytes(), equalTo(recoveredBytes));
+        assertThat(recoveryState.getIndex().recoveredBytes(), equalTo(recoveredBytes));
     }
 
     public void testFilesStoredInThePersistentCacheAreMarkedAsReusedInRecoveryState() throws Exception {
@@ -198,6 +200,7 @@ public void testFilesStoredInThePersistentCacheAreMarkedAsReusedInRecoveryState(
         assertThat(physicalCacheSize, equalTo(expectedPhysicalCacheSize));
         assertThat(physicalCacheSize + inMemoryCacheSize, equalTo(recoveryState.getIndex().reusedBytes()));
         assertThat("Expected to recover 100% of files", recoveryState.getIndex().recoveredBytesPercent(), equalTo(100.0f));
+        assertThat(recoveryState.getIndex().recoveredFromSnapshotBytes(), equalTo(0L));
 
         for (RecoveryState.FileDetail fileDetail : recoveryState.getIndex().fileDetails()) {
             assertThat(fileDetail.name() + " wasn't mark as reused", fileDetail.reused(), equalTo(true));

x-pack/plugin/searchable-snapshots/src/main/java/org/elasticsearch/xpack/searchablesnapshots/store/SearchableSnapshotDirectory.java

@@ -532,7 +532,7 @@ private void prewarmCache(ActionListener<Void> listener) {
                         if (persistentCacheLength == file.length()) {
                             recoveryState.markIndexFileAsReused(file.physicalName());
                         } else {
-                            recoveryState.getIndex().addRecoveredBytesToFile(file.physicalName(), file.partBytes(part));
+                            recoveryState.getIndex().addRecoveredFromSnapshotBytesToFile(file.physicalName(), file.partBytes(part));
                         }
 
                         logger.trace(