Reorganize `well_known_note` module

We should reorganize the `well_known_note` module, creating a new submodule for each well-known note:
```text
note
└── well_known_notes
├── mod.rs
├── p2id.rs
├── p2ide.rs
├── swap.rs
└── etc.
```

_Originally posted by @bobbinth in https://github.com/0xMiden/miden-base/pull/1998#discussion_r2480544373_