feat: add `CharmReconciler` and `Components`

[ca-scribner]

This implements:

• a reusable charm reconcile function (CharmReconciler)
• Component, an abstraction for any piece of logic in a charm
• several generic Component subclasses for Kubernetes resources, Pebble containers, and some other situations

These are documented in:

• ./src/charmed_kubeflow_chisme/components/README.md, which gives a general overview
• ./src/charmed_kubeflow_chisme/components/how-to/, has several how-to guides for using these tools
• this spec

Tests are included, but during development this was also tested live with the following prototype charms:

• https://github.com/canonical/kfp-operators/pull/264
• https://github.com/canonical/kfp-operators/pull/268
• https://github.com/canonical/kfp-operators/pull/280
• https://github.com/canonical/kfp-operators/pull/287
• https://github.com/canonical/kfp-operators/pull/288