Merge dev into next (#5857)

.changesets/feat_geal_v8_heap_statistics.md

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+### Add V8 heap usage metrics ([PR #5781](https://github.com/apollographql/router/pull/5781))
+
+The router supports new gauge metrics for tracking heap memory usage of the V8 Javascript engine:
+- `apollo.router.v8.heap.used`: heap memory used by V8, in bytes
+- `apollo.router.v8.heap.total`: total heap allocated by V8, in bytes
+
+By [@Geal](https://github.com/Geal) in https://github.com/apollographql/router/pull/5781

.changesets/feat_tninesling_cost_directives.md

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+### Account for demand control directives when scoring operations ([PR #5777](https://github.com/apollographql/router/pull/5777))
+
+When scoring operations in the demand control plugin, utilize applications of `@cost` and `@listSize` from the supergraph schema to make better cost estimates.
+
+For expensive resolvers, the `@cost` directive can override the default weights in the cost calculation.
+
+```graphql
+type Product {
+  id: ID!
+  name: String
+  expensiveField: Int @cost(weight: 20)
+}
+```
+
+Additionally, if a list field's length differs significantly from the globally-configured list size, the `@listSize` directive can provide a tighter size estimate.
+
+```graphql
+type Magazine {
+  # This is assumed to always return 5 items
+  headlines: [Article] @listSize(assumedSize: 5)
+
+  # This is estimated to return as many items as are requested by the parameter named "first"
+  getPage(first: Int!, after: ID!): [Article]
+    @listSize(slicingArguments: ["first"])
+}
+```
+
+By [@tninesling](https://github.com/tninesling) in https://github.com/apollographql/router/pull/5777

.changesets/feat_update_federation.md

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+### Update federation to 2.8.3 ([PR #5781](https://github.com/apollographql/router/pull/5781))
+
+> [!IMPORTANT]
+> If you have enabled [Distributed query plan caching](https://www.apollographql.com/docs/router/configuration/distributed-caching/#distributed-query-plan-caching), this release changes the hashing algorithm used for the cache keys.  On account of this, you should anticipate additional cache regeneration cost when updating between these versions while the new hashing algorithm comes into service.
+
+This updates the router from federation version 2.8.1 to 2.8.3, with a [fix for fragment generation](https://github.com/apollographql/federation/pull/3043).
+
+By [@Geal](https://github.com/Geal) in https://github.com/apollographql/router/pull/5781

.changesets/fix_geal_subgraph_error_path.md

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+### set the subgraph error path if not present ([PR #5773](https://github.com/apollographql/router/pull/5773))
+
+This fixes subgraph response conversion to set the error path in all cases. For some network level errors, the subgraph service was not setting the path
+
+By [@Geal](https://github.com/Geal) in https://github.com/apollographql/router/pull/5773