test: Bump timeouts in feature_index_prune and wallet_importdescriptors

Timeout issues where encountered when running functional tests with `--jobs=16 --extended`.

Line in `feature_index_prune.py` took 101.6s, 96.6s, 103.0s across 3 runs on my machine, default limit is 60.

Line in the `wallet_importdescriptors.py --descriptors` took 5.4s, 5.7s, 6.0s across 3 runs.

test/functional/feature_index_prune.py

@@ -31,7 +31,7 @@ class FeatureIndexPruneTest(BitcoinTestFramework):
         expected_stats = {
             'coinstatsindex': {'synced': True, 'best_block_height': height}
         }
-        self.wait_until(lambda: self.nodes[1].getindexinfo() == expected_stats)
+        self.wait_until(lambda: self.nodes[1].getindexinfo() == expected_stats, timeout=150)
 
         expected = {**expected_filter, **expected_stats}
         self.wait_until(lambda: self.nodes[2].getindexinfo() == expected)