Move ExecutionObserver to folly/executors

Summary:
The following targets were moved to folly/executors:
```
//folly/experimental:execution_observer
```

`arc f` was applied

This is a codemod. It was automatically generated and will be landed once it is approved and tests are passing in sandcastle.
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p:ad_meeo.folly

Reviewed By: yfeldblum, Orvid

Differential Revision: D58028038

fbshipit-source-id: 0fd1dfb349421d61e9f49eb546b4c4cc0d0c0c19

quic/somerge_defs.bzl

@@ -2,7 +2,7 @@
 
 Generated by xplat/cross_plat_devx/somerge_maps/compute_merge_maps.py
 
-@generated SignedSource<<634c5cbf3280543f0cad57e52e06c074>>
+@generated SignedSource<<b9b1e57905105573437dc1442ccf3343>>
 """
 
 # Entry Points:
@@ -46,6 +46,8 @@ QUIC_NATIVE_LIBRARY_MERGE_MAP = [
     "//xplat/quic/common/events:quic_timerAndroidAndroid",
     "//xplat/quic/common/third-party:better_enumsAndroid",
     "//xplat/quic/common/third-party:better_enumsAndroidAndroid",
+    "//xplat/quic/common/third-party:tiny_optionalAndroid",
+    "//xplat/quic/common/third-party:tiny_optionalAndroidAndroid",
     "//xplat/quic/common/udpsocket:folly_async_udp_socketAndroid",
     "//xplat/quic/common/udpsocket:folly_async_udp_socketAndroidAndroid",
     "//xplat/quic/common/udpsocket:quic_async_udp_socketAndroid",
@@ -66,6 +68,8 @@ QUIC_NATIVE_LIBRARY_MERGE_MAP = [
     "//xplat/quic/common:looperAndroidAndroid",
     "//xplat/quic/common:network_dataAndroid",
     "//xplat/quic/common:network_dataAndroidAndroid",
+    "//xplat/quic/common:optionalAndroid",
+    "//xplat/quic/common:optionalAndroidAndroid",
     "//xplat/quic/common:small_collectionsAndroid",
     "//xplat/quic/common:small_collectionsAndroidAndroid",
     "//xplat/quic/common:socket_utilAndroid",