perf(cosmos): strip unused fields from partition key range cache

Strip 9 unused fields from partition key range dicts after fetching
from the service. CollectionRoutingMap only uses 4 fields (id,
minInclusive, maxExclusive, parents) but the service returns 13.

Reduces per-range dict memory by ~40%, measured with tracemalloc
on 150 CosmosClient instances with PPCB enabled:

Test setup:
- Account: ~100 physical partitions, 2 regions, multi-write
- Tool: tracemalloc (retained memory)
- Operations: 1 read_item + 1 upsert_item per client

Results (current memory, MB):

| Clients | 4.15.0 PPCB=True | Patched PPCB=True | PPCB=false | Savings |
|---------|-----------------|------------------|-----------|---------|
|       1 |           14.3  |            14.3  |      14.0 |  -0.0   |
|      25 |           23.0  |            20.5  |      17.9 |  -2.5   |
|      50 |           31.9  |            27.4  |      21.7 |  -4.5   |
|     100 |           44.9  |            39.9  |      29.4 |  -4.9   |
|     150 |           63.8  |            52.9  |      36.4 | -10.9   |

PPCB overhead reduction:

| Clients | Before | After  | Reduction |
|---------|--------|--------|-----------|
|      25 | 5.1 MB | 2.6 MB | -48%      |
|      50 |10.3 MB | 5.7 MB | -44%      |
|     100 |15.4 MB |10.5 MB | -31%      |
|     150 |27.4 MB |16.5 MB | -39%      |

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: tvaron3

sdk/cosmos/azure-cosmos/azure/cosmos/_routing/aio/routing_map_provider.py

@@ -97,6 +97,12 @@ async def init_collection_routing_map_if_needed(
             # causing the partitionKeyRanges to have both the children ranges and their parents. Therefore, we need
             # to discard the parent ranges to have a valid routing map.
             collection_pk_ranges = list(PartitionKeyRangeCache._discard_parent_ranges(collection_pk_ranges))
+            # Strip fields not used by CollectionRoutingMap to reduce memory footprint
+            _KEEP = frozenset({"id", "minInclusive", "maxExclusive", "parents"})
+            collection_pk_ranges = [{k: v for k, v in r.items() if k in _KEEP} for r in collection_pk_ranges]
+            # Strip fields not used by CollectionRoutingMap to reduce memory footprint
+            _KEEP = frozenset({"id", "minInclusive", "maxExclusive", "parents"})
+            collection_pk_ranges = [{k: v for k, v in r.items() if k in _KEEP} for r in collection_pk_ranges]
             collection_routing_map = CollectionRoutingMap.CompleteRoutingMap(
                 [(r, True) for r in collection_pk_ranges], collection_id
             )

sdk/cosmos/azure-cosmos/azure/cosmos/_routing/routing_map_provider.py

@@ -82,6 +82,12 @@ def init_collection_routing_map_if_needed(
             # causing the partitionKeyRanges to have both the children ranges and their parents. Therefore, we need
             # to discard the parent ranges to have a valid routing map.
             collection_pk_ranges = list(PartitionKeyRangeCache._discard_parent_ranges(collection_pk_ranges))
+            # Strip fields not used by CollectionRoutingMap to reduce memory footprint
+            _KEEP = frozenset({"id", "minInclusive", "maxExclusive", "parents"})
+            collection_pk_ranges = [{k: v for k, v in r.items() if k in _KEEP} for r in collection_pk_ranges]
+            # Strip fields not used by CollectionRoutingMap to reduce memory footprint
+            _KEEP = frozenset({"id", "minInclusive", "maxExclusive", "parents"})
+            collection_pk_ranges = [{k: v for k, v in r.items() if k in _KEEP} for r in collection_pk_ranges]
             collection_routing_map = CollectionRoutingMap.CompleteRoutingMap(
                 [(r, True) for r in collection_pk_ranges], collection_id
             )