️🛠 - Implement preset system

[maxwellmattryan]

Description

Presets are a significant part of any larger, more complex audio plugin. There is no need to duplicate this logic across projects, so it should be implemented once and re-used.

One unknown is what is implied in terms of design and code organization since presets will be interacted with through a menu, i.e. a UI component (that is likely to WebView-based).

The backend will need to expose the following functions for the frontend:

• selectPreset - selects or deselects a preset to be the currently selected one
• savePreset - saves a new or updates an existing preset
• deletePreset - deletes a preset file at a given file path
• getPreset - retrieves a particular preset (based on file name/path)
• getPresets - retrieves all of the presets
• getPluginMetadata - provides metadata about the plugin e.g., name, version, company, copyright, etc.
• revealPresetLocation - opens the preset's containing folder in the native OS file explorer

I'll probably also need to add a method or two to the ParameterManager in nectar, namely getStateAsXml or similar which saves all of the current parameter values to an XML File.

Requirements

TBD