fix: proxy initialization reentrancy

[gabririgo]

As described in this RBIP, a proxy initialization could be reentered. While side effects are unclear, it would be best to add a non-reentrancy modifier in the implementations.
Interestingly, this issue was never spotted by OpenZeppelin Defender.

[gabririgo]

view methods to an external contract execute a staticcall and therefore pool initialization cannot be reentered in the context of rigoblock. Although adding a non-reentrant modifier would future-proof the proxy initialization, there is no apparent need for a non-view call to an external contract during pool initialization, therefore it is pointless to add gas cost to pool deployment.