Please review updated website documentation on "Component testing"

[rbygrave]

Refer: https://avaje.io/inject/#component-testing

I've updated this part of the documentation fairly radically. If people can review that and provide feedback that would be awesome.

Thanks.

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Documentation that still is missing:

• @Prototype
• AOP Aspects

Plus [design] documentation for, Why avaje-inject does not have ...

• Does not have "lazy singleton"
• Does not have @Value (why we expect to do external configuration differently including dynamic configuration)
• Does not have "refreshable context"