Add a class TorsStreamIsolationCredentialsGenerator that generates
unique credentials based on a randomly generated session prefix
and an atomic counter.
This makes sure that different launches of the application won't share
the same credentials, and thus circuits, even in edge cases.
Example with `-debug=proxy`:
```
2025-03-31T16:30:27Z [proxy] SOCKS5 sending proxy authentication 0afb2da441f5c105-0:0afb2da441f5c105-0
2025-03-31T16:30:31Z [proxy] SOCKS5 sending proxy authentication 0afb2da441f5c105-1:0afb2da441f5c105-1
```
Thanks to hodlinator for the idea.
Allow the callers of `CreateSock()` to pass all 3 arguments to the
`socket(2)` syscall. This makes it possible to create sockets of
any domain/type/protocol.
This is an extraction of ArgsManager related functions from util/system
into their own common file.
Config file related functions are moved to common/config.cpp.
The background of this commit is an ongoing effort to decouple the
libbitcoinkernel library from the ArgsManager. The ArgsManager belongs
into the common library, since the kernel library should not depend on
it. See doc/design/libraries.md for more information on this rationale.
