Implement LNProxy-like privacy

Wallet providers with outsized view of the network (custodial wallets such as Wallet of Satoshi, or providers that handle routing, such as Phoenix Wallet -> acinq) can determine a btcpayserver's e-shop turnover and number of transactions by scanning and saving public keys. There is no need to give these providers this information.

BTCPayServer could implement a mechanism similar to LNProxy to create random public keys and proxy the payments to make this type of surveillance a little bit more difficult.

https://github.com/lnproxy/lnproxy

Start by reviewing the issue requirements and the linked LNProxy project to understand the proposed privacy mechanism. The payload names no files, tests, entry points, or acceptance criteria, so the implementation scope and definition of done need to be established before work begins.

Written by the indexing model from the issue text.