net: Implement canceling of all async operations in FileStream.

tools/valgrind/memcheck/suppressions.txt

Index: tools/valgrind/memcheck/suppressions.txt
diff --git a/tools/valgrind/memcheck/suppressions.txt b/tools/valgrind/memcheck/suppressions.txt
index e9648ae37d74036eb471224c3edd022569804a0a..ed8c828c2d50b25183251efb857ee52b20d05561 100644
--- a/tools/valgrind/memcheck/suppressions.txt
+++ b/tools/valgrind/memcheck/suppressions.txt
@@ -6023,6 +6023,21 @@
    fun:_ZN2v88internalL21Builtin_HandleApiCallENS0_12_GLOBAL__N_116BuiltinArgumentsILNS0_21BuiltinExtraArgumentsE1EEEPNS0_7IsolateE
 }
 {
+   FileStream::Context can leak through WorkerPool by design
+   Memcheck:Leak
+   fun:_Znw*
+   fun:_ZN3net10FileStreamC1EPNS_6NetLogE
+   ...
+}
+{
+   Tasks posted to WorkerPool can leak by design
+   Memcheck:Leak
+   fun:_Znw*
+   fun:_ZN4base8internal20PostTaskAndReplyImpl16PostTaskAndReplyERKN15tracked_objects8LocationERKNS_8CallbackIFvvEEESA_
+   fun:_ZN4base10WorkerPool16PostTaskAndReplyERKN15tracked_objects8LocationERKNS_8CallbackIFvvEEES9_b
+   ...
+}
+{
    bug_149748b
    Memcheck:Unaddressable
    ...