fix bootstrap pipeline prechecking of blocks

Context

This MR fixes a bug (introduced by !6335 (merged)) in the bootstrap pipeline that allowed applying a block without prechecking it first. It also ensures that a block is prechecked before being applied.

Manually testing the MR

CI green

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• n/a Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
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