[Brook] Made the runtime a client object and shared Producer writers.

CHANGELOG.md

@@ -128,3 +128,21 @@
   alone, so a read always moves on.
 - The Redis and memory Stores read no `to_offset` or `wake_only`. A read with one fails with
   `stream_unsupported`, since only the native backend serves them.
+- The runtime is a plain object with no Core trait. A bridge builds it per client and calls
+  `StreamExtension::call` with a method name and proto bytes. An error has `code()` and
+  `details()`, the encoded `StreamErrorDetails`. The crate no longer depends on
+  `temporalio-sdk-core`, and it pins `temporalio-common` at sdk-rust Brook c7 `b565c433`.
+- The handles of one Producer epoch on one Stream share one writer. Each `OpenWriter` adds a
+  handle, and each `CloseWriter` or the new `FreeWriter` releases one. `FreeWriter` and
+  `StreamExtension::free_writer` release with no wait, for a handle that lang drops. The last
+  handle drops the writer, so a process keeps no writer that no handle uses.
+- Every writer in a process takes its batch `sequence` from one counter, so a writer opened again
+  after its close goes on above its earlier batches. The map of closed writers' sequences is
+  gone, and it no longer grows for the life of the process.
+- `ids::named_client_producer_id` makes `client:<name>`, a client Producer id that the caller
+  keeps across restarts. With the caller's epoch in `attempt`, a new incarnation fences the
+  earlier one.
+- A client Producer's newer epoch fences its earlier epochs but writes no `Superseded` item and
+  withdraws nothing, in the Redis script, the memory Store and the reader rule. The withdrawal
+  rule stays for Workflow, Local Activity and Activity Producers. `testdata/withdrawals.json` has
+  the case.