Update snap packaging for v3.3.6 with CMake and core22

Migrate from autotools to cmake plugin, upgrade base from core18 to
core22, point source to local git repo instead of stale v3.3.5 tarball,
update PCRE3 to PCRE2, and update runtime library packages for Ubuntu
22.04.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: madeye

snap/snapcraft.yaml

@@ -1,6 +1,6 @@
-base: core18
+base: core22
 name: shadowsocks-libev
-version: 3.3.6-1
+version: '3.3.6'
 summary: libev port of shadowsocks
 description: |
   Shadowsocks-libev is a lightweight and secure SOCKS5 proxy for embedded
@@ -13,57 +13,63 @@ confinement: strict
 
 apps:
   ss-local:
-    command: bin/ss-local
+    command: usr/bin/ss-local
     plugs: [network, network-bind]
 
   ss-local-daemon:
-    command: bin/ss-local
+    command: usr/bin/ss-local
     daemon: simple
     plugs: [network, network-bind]
 
   ss-server:
-    command: bin/ss-server
+    command: usr/bin/ss-server
     plugs: [network, network-bind]
 
   ss-server-daemon:
-    command: bin/ss-server
+    command: usr/bin/ss-server
     daemon: simple
     plugs: [network, network-bind]
 
   ss-redir:
-    command: bin/ss-redir
+    command: usr/bin/ss-redir
     plugs: [network, network-bind]
 
   ss-tunnel:
-    command: bin/ss-tunnel
+    command: usr/bin/ss-tunnel
     plugs: [network, network-bind]
 
   ss-manager:
-    command: bin/ss-manager
+    command: usr/bin/ss-manager
     plugs: [network]
 
-passthrough:
-  layout:
-    /etc/shadowsocks-libev:
-      bind: $SNAP_COMMON/etc/shadowsocks-libev
+layout:
+  /etc/shadowsocks-libev:
+    bind: $SNAP_COMMON/etc/shadowsocks-libev
 
 parts:
- shadowsocks-libev:
-    plugin: autotools
-    source: https://github.com/shadowsocks/shadowsocks-libev/releases/download/v3.3.5/shadowsocks-libev-3.3.5.tar.gz
+  shadowsocks-libev:
+    plugin: cmake
+    source: .
+    source-type: git
+    cmake-parameters:
+      - -DCMAKE_INSTALL_PREFIX=/usr
+      - -DCMAKE_BUILD_TYPE=Release
+      - -DWITH_DOC_MAN=OFF
+      - -DBUILD_TESTING=OFF
     build-packages:
-      - libpcre3-dev
-      - asciidoc
-      - xmlto
+      - libpcre2-dev
       - libev-dev
       - libc-ares-dev
       - libmbedtls-dev
       - libsodium-dev
     stage-packages:
       - libc-ares2
       - libev4
-      - libmbedtls10
+      - libmbedcrypto7
+      - libmbedtls14
+      - libmbedx509-1
+      - libpcre2-8-0
       - libsodium23
     override-build: |
-      snapcraftctl build
+      craftctl default
       rm -rf $SNAPCRAFT_PART_INSTALL/usr/share/doc