[all] Do not init twice

[damienmarchal]

Entering into init() is only allowed if the component is in a non ready state. Implement basic checking on two problematic component that emits warning/error messages when emitted twice.

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Reviewers will merge this pull-request only if

• it builds with SUCCESS for all platforms on the CI.
• it does not generate new warnings.
• it does not generate new unit test failures.
• it does not generate new scene test failures.
• it does not break API compatibility.
• it is more than 1 week old (or has fast-merge label).

[alxbilger]

[ci-build][with-all-tests]

[damienmarchal]

[ci-build][with-scene-tests]

[hugtalbot]

thanks for the PR @damienmarchal interesting we could add the flag for discussion at next dev meeting maybe?

the state "Loading" could be in the constructor of any BaseObject .. to be discussed