Replace Boost.Asio with standalone Asio library

We had to add an even hackier hack now to get Boost.Process to
interoperate with Asio's IO contexts. This will be replaced later when
we replace Boost.Process.

src/plugin/bridges/vst3.cpp

@@ -27,7 +27,7 @@ using namespace std::literals::string_literals;
 Vst3PluginBridge::Vst3PluginBridge()
     : PluginBridge(
           PluginType::vst3,
-          [](boost::asio::io_context& io_context, const PluginInfo& info) {
+          [](asio::io_context& io_context, const PluginInfo& info) {
               return Vst3Sockets<std::jthread>(
                   io_context,
                   generate_endpoint_base(info.native_library_path_.filename()
@@ -415,7 +415,7 @@ Vst3PluginBridge::~Vst3PluginBridge() noexcept {
         // Drop all work make sure all sockets are closed
         plugin_host_->terminate();
         io_context_.stop();
-    } catch (const boost::system::system_error&) {
+    } catch (const std::system_error&) {
         // It could be that the sockets have already been closed or that the
         // process has already exited (at which point we probably won't be
         // executing this, but maybe if all the stars align)