feat!: Make resource creation be on demand to enable testing [PROPOSAL]

[luanpotter]

Description

Make resource creation be on demand to enable testing.

Basically changes how the Resource class work:

• resources are lazily loaded
• the Resource class is responsible for re-creating resources when needed
• children just provide the recreateResource boolean

Checklist

• [x] I have followed the Contributor Guide when preparing my PR.
• [x] I have updated/added tests for ALL new/updated/fixed functionality.
• [x] I have updated/added relevant documentation in docs and added dartdoc comments with ///.
• [x] I have updated/added relevant examples in examples or docs.

Breaking Change?

• [ ] Yes, this PR is a breaking change.
• [x] No, this PR is not a breaking change.