feat: add Default impls and new() constructors

[roderickvd]

As I noticed PipeWire had a curious choice of #[default] Roles, I did a sweep across all hosts to implement Default where it makes sense, add a new() constructor where idiomatic, and check the sanity of existing Default implementations.

These are not defined on the trait, so use it for platform-specific convenience rather than expecting it works cross-platform (it doesn't).

Additionally, tidy up the derives particularly on non-public types in order to reduce compile times.

[Copilot]

Pull request overview

This PR adds Default implementations and lightweight new() constructors across several backend-specific types, and standardizes enum defaults where appropriate (including a small behavioral fix in AudioWorklet device enumeration). These changes are platform conveniences (not trait-level guarantees) and primarily improve ergonomics for backend-specific usage.

Changes:

• Implement Default for core enums (BufferSize, SupportedBufferSize) and multiple backend Host/Device types; add new() constructors where idiomatic.
• Adjust backend code to construct devices via Device::new() / Device::default() consistently.
• Fix AudioWorklet Devices::default() to only enumerate when Host::is_available().

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/lib.rs	Adds Default for BufferSize and SupportedBufferSize with explicit default variants.
src/host/webaudio/mod.rs	Adds Default for Device/Host, adds Device::new(), and uses it in iteration/default device selection.
src/host/wasapi/mod.rs	Adds Default for WASAPI Host.
src/host/pipewire/device.rs	Changes Role default to Sink; adds Default for NodeOverrides and introduces NodeOverrides::new().
src/host/null/mod.rs	Adds Default for several null-backend types and introduces new() constructors.
src/host/coreaudio/macos/mod.rs	Adds Default for CoreAudio (macOS) Host.
src/host/coreaudio/ios/mod.rs	Adds Default for iOS CoreAudio Device/Host and adds Device::new().
src/host/coreaudio/ios/enumerate.rs	Updates enumeration/default-device construction to use Device::new() / Device::default().
src/host/audioworklet/mod.rs	Adds Default for Device/Host, adds Device::new(), and fixes Devices::default() gating on availability.
src/host/asio/stream.rs	Derives Default for TimeBase and simplifies TimeBase::new() to delegate to default().
src/host/aaudio/mod.rs	Adds Default for Host/Device, adds Device::new(), and updates fallback/default device creation.
src/host/aaudio/java_interface/definitions.rs	Adds Default to AudioDeviceType with Unknown as the default variant.
CHANGELOG.md	Documents the newly added Default/new() conveniences and the AudioWorklet enumeration fix.

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[Copilot]

Pull request overview

Copilot reviewed 17 out of 17 changed files in this pull request and generated 1 comment.