[backport] bump libevent to 2.1.11 in depends

Summary
---

This is a backport of bitcoin/bitcoin#17008

this doesn't need patches on Android anymore like 2.1.8 did.

Test plan
---

* `ninja all check-all`
* Do a cross compilation build and test, see
  https://docs.bitcoincashnode.org/depends/#usage

depends/packages/libevent.mk

@@ -1,8 +1,8 @@
 package=libevent
-$(package)_version=2.1.8-stable
+$(package)_version=2.1.11-stable
 $(package)_download_path=https://github.com/libevent/libevent/archive/
 $(package)_file_name=release-$($(package)_version).tar.gz
-$(package)_sha256_hash=316ddb401745ac5d222d7c529ef1eada12f58f6376a66c1118eee803cb70f83d
+$(package)_sha256_hash=229393ab2bf0dc94694f21836846b424f3532585bac3468738b7bf752c03901e
 
 define $(package)_preprocess_cmds
   ./autogen.sh

doc/dependencies.md

@@ -19,7 +19,7 @@ These dependencies are required:
 | HarfBuzz-NG |  |  |  |  |  |  |  |
 | help2man |  |  |  |  |  | Manpages | Optional, used for building manpages |
 | jemalloc | [5.2.1](https://github.com/jemalloc/jemalloc/releases) |  |  |  |  |
-| libevent | [2.1.8-stable](https://github.com/libevent/libevent/releases) | 2.0.22 | No |  |  |  Networking       | OS independent asynchronous networking |
+| libevent | [2.1.11-stable](https://github.com/libevent/libevent/releases) | 2.0.22 | No |  |  |  Networking       | OS independent asynchronous networking |
 | libjpeg |  |  |  |  | Yes |  |  |
 | libpng |  |  |  |  | Yes |  |  |
 | MiniUPnPc | [2.0.20180203](http://miniupnp.free.fr/files) | 1.5 | No |  |  | UPnP Support     | Firewall-jumping support |