vst3: components with no audio buses fail the Steinberg validator (param-only objects, analyzers)

[jcelerier]

59 of 84 example .vst3s fail exactly one Steinberg-validator test:

ERROR: This component does not export any buses!!!

Two sub-cases:

• parameter-only test/utility objects (no audio I/O at all) — arguably shouldn't be built as VST3, or need a synthetic event bus;
• analyzers with real audio inputs (e.g. avnd_essentia_entropy, which takes an audio input) also report 0 In(s) => 0 Out(s) — the vst3 audio_bus_info seems to miss their input port shape, which is a real bug.

Also: avnd_test_audio_variable.vst3 crashes the validator outright (no result).

Repro: build the SDK validator target (fetched SDK) and run it over build/*/vst3/*.vst3.

[jcelerier]

Analyzers fixed on the avendish-ui branch: channel_port_processor's audio_bus_info used the bus-port introspection (empty for mono .channel ports) instead of the channel-port introspection, in both the vst3 and clap bindings; the vst3 no-concept-matched default now also derives buses from the wrappers' channel counts. avnd_essentia_entropy.vst3 is 47/47 on the Steinberg validator, and avnd_test_audio_variable.vst3's crash is fixed (unwired request_channels, see #153).

Remaining scope of this issue: parameter-only test/utility objects (no audio or event I/O at all) still fail the validator's ≥1-bus expectation — that is by design of those objects; options are a synthetic event bus or not shipping them as VST3.