refactor(Output): Lazy-load RestPlugin only when Compiler=Rest env var is set

Change RestPlugin from eager import to lazy loading, loading the plugin dynamically only when Compiler=Rest environment variable is explicitly set. This avoids importing RestPlugin (and its node:fs dependencies) during normal ESBuild builds.

- Update Source/ESBuild/Output.ts and Configuration/ESBuild/Output.js to conditionally import RestPlugin
- Replace `createRestPluginIfEnabled()` with lazy import: `await import("./RestPlugin.js").then((M) => M.createRestPluginIfEnabled())`
- Simplify filter from `(plugin) => plugin !== null` to `Boolean`
- Reformat all ESBuild configuration files for consistent style
- Update prepublishOnly.sh build commands with correct file patterns and paths

This improves build performance by avoiding unnecessary module resolution when using the default ESBuild compiler.

Author: NikolaRHristov