Move the hard realtime constant to Plugin

Since we could indeed just add the `|OnlyRT` category to the VST3
plugin.

BREAKING_CHANGES.md

@@ -6,6 +6,12 @@ new and what's changed, this document lists all breaking changes in reverse
 chronological order. If a new feature did not require any changes to existing
 code then it will not be listed here.
 
+## [2022-07-05]
+
+- The `ClapPlugin::CLAP_HARD_REALTIME` constant was moved to the general
+  `Plugin` trait as `Plugin::HARD_REALTIME_ONLY` and best-effort support for
+  VST3 was added.
+
 ## [2022-07-04]
 
 - There is a new `NoteEvent::Choke` event the host can send to a plugin to let

src/plugin.rs

@@ -80,6 +80,11 @@ pub trait Plugin: Default + Send + Sync + 'static {
     /// every 64 samples.
     const SAMPLE_ACCURATE_AUTOMATION: bool = false;
 
+    /// If this is set to true, then the plugin will report itself as having a hard realtime
+    /// processing requirement when the host asks for it. Supported hosts will never ask the plugin
+    /// to do offline processing.
+    const HARD_REALTIME_ONLY: bool = false;
+
     /// The plugin's parameters. The host will update the parameter values before calling
     /// `process()`. These parameters are identified by strings that should never change when the
     /// plugin receives an update.
@@ -201,13 +206,6 @@ pub trait ClapPlugin: Plugin {
     /// Keywords describing the plugin. The host may use this to classify the plugin in its plugin
     /// browser.
     const CLAP_FEATURES: &'static [ClapFeature];
-
-    /// If this is set to true, then the plugin will report itself as having a hard realtime
-    /// processing requirement when the host asks for it. Supported hosts will never ask the plugin
-    /// to do offline processing.
-    // TODO: Supposedly VST3 also has something similar if you add an `|OnlyRT` category. We should
-    //       move this to the Plugin trait and use that for VST3
-    const CLAP_HARD_REALTIME: bool = false;
 }
 
 /// Provides auxiliary metadata needed for a VST3 plugin.

src/wrapper/clap/wrapper.rs

@@ -2934,7 +2934,7 @@ impl<P: ClapPlugin> Wrapper<P> {
     unsafe extern "C" fn ext_render_has_hard_realtime_requirement(
         _plugin: *const clap_plugin,
     ) -> bool {
-        P::CLAP_HARD_REALTIME
+        P::HARD_REALTIME_ONLY
     }
 
     unsafe extern "C" fn ext_render_set(