feat: added handling for all plugin command functionality

[eddie-knight]

This PR moves all command logic that is common to plugins into SDK functions.

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This pull request introduces a new command plugin system for the Privateer project. The changes include adding a new command package, creating a Plugin type, and defining several command functions. Additionally, a new constructor function for the Vessel type is added in the pluginkit package.

Command Plugin System:

• command/plugin.go: Added a new command package with a Plugin type and functions to create and manage plugin commands, including runCommand, debugCommand, and versionCommand.

Vessel Constructor:

• pluginkit/vessel.go: Introduced a NewVessel constructor function to initialize a Vessel with required parameters such as name, armory, initializer, and requiredVars.