feat: implementing Startable and propagating stop()

[curtis-h]

Description:

Issue: #225

Agent.stop() now chains into Pluto.stop() which chains to Store.stop().

• Created Startable namespace to define and share implementation.
• Pluto interface extends Startable.IController
• Pluto/rxdb/Store added stop() fn
• Pluto implementation extends Startable.Controller
• Pollux implementation extends Startable.Controller
• Agents
  • replaced duplicated AgentState with Startable.State
  • handled start and stop
• added functional tests

Checklist:

• My PR follows the contribution guidelines of this project
• My PR is free of third-party dependencies that don't comply with the Allowlist
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• I have checked the PR title to follow the conventional commit specification

[github-actions]

Lines	Statements	Branches	Functions
	78.09% (3740/4789)	68.51% (1726/2519)	81.95% (890/1086)

[coveralls]

coverage: 74.614% (+0.6%) from 74.029%
when pulling 66fbc7b on feature/225-startables
into 6745ea3 on main.

[coveloper]

Can this be merged?

[elribonazo]

After rebase @curtis-h we waited enough time, I would propose to merge yeah!