perf: reuse ResizeArray buffer in chunkBy and chunkByAsync

Previously, each time a new chunk was started in chunkBy/chunkByAsync,
a fresh ResizeArray was allocated. Since ToArray() already captures an
independent copy of the data, the internal buffer can be safely reused
by calling Clear() instead of constructing a new ResizeArray.

This eliminates one heap allocation per chunk boundary, reducing GC
pressure for sequences with many distinct runs.

5017 tests pass, 2 skipped.

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

Author: github-actions[bot]

release-notes.txt

@@ -2,6 +2,7 @@
 Release notes:
 
 1.0.0
+    - perf: TaskSeq.chunkBy and chunkByAsync reuse the ResizeArray buffer between chunks, reducing allocations on sequences with many chunk boundaries
     - fixes: TaskSeq.insertAt, insertManyAt, removeAt, removeManyAt, updateAt now raise ArgumentNullException (not NullReferenceException) when given a null source; insertManyAt also validates the values argument
     - refactor: simplify lengthBy and lengthBeforeMax to use while! and remove the redundant mutable 'go' and initial MoveNextAsync
     - adds TaskSeq.distinctUntilChangedWith and TaskSeq.distinctUntilChangedWithAsync, #345

src/FSharp.Control.TaskSeq/TaskSeqInternal.fs

@@ -1754,7 +1754,7 @@ module internal TaskSeqInternal =
                         currentChunk.Add item
                     else
                         yield prevKey, currentChunk.ToArray()
-                        currentChunk <- ResizeArray<'T>()
+                        currentChunk.Clear() // reuse backing array; ToArray() already captured a snapshot
                         currentChunk.Add item
                         maybeCurrentKey <- ValueSome key
 
@@ -1782,7 +1782,7 @@ module internal TaskSeqInternal =
                         currentChunk.Add item
                     else
                         yield prevKey, currentChunk.ToArray()
-                        currentChunk <- ResizeArray<'T>()
+                        currentChunk.Clear() // reuse backing array; ToArray() already captured a snapshot
                         currentChunk.Add item
                         maybeCurrentKey <- ValueSome key