Fix the starknet libfuncs' bugs. (#694)

* Refactor starknet libfunc impls to use the block extension trait.

* Fix stuff.

* Fix stuff.

* Fix alloca, load and store operations on `BlockExt`.

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Co-authored-by: Pedro Fontana <fontana.pedro93@gmail.com>
Co-authored-by: Edgar <git@edgarluque.com>

Author: 3 people