Introduce ability to limit which Safe addresses the TXS operates on

[DefiDebauchery]

What is needed?

Limit TXS indexing and activity to specified Safe addresses.

Background

Teams may want to run local/internal instances of the Safe Transaction Service, but not want to spend the resources indexing every Safe ever created, which would not be relevant to them.

Ideally, such a setting would also limit ERC20 indexing to only pertain to the addresses in question, resulting in much faster initial indexing, and lighter-weight TXS overall.

Related issues

I finally unearthed a question I had asked on how to initially do this. While the line referenced is still relevant, this was also from three years ago, and I'm unsure if there are other places where such a central configuration would be useful

https://ethereum.stackexchange.com/questions/120117/configuring-gnosis-txs-to-only-care-about-specific-safes

Notes

While a configuration entry (config/base.py?) would be good for initial population, an admin route to selectively add additional or future Safes without restarting the running instance could be useful, if possible.