Move the implementation of BDA::wipe into the static header module

[mulkieran]

I think that BDA::wipe is invoked from outside the metadata module, so the method itself should be left. A new method should be created inside the static_header module.

Here's the new proposal:

1. Hoist the device_identifiers method right out of the BDA implementation and into the module top-level. This can be done by defining it, as a public method, in metadata/mod.rs. A lot of callers which currently call BDA::device_identifiers will need to be updated accordingly. Internal tests which call device_identifiers should be updated to call StaticHeader::setup instead.

2. Simultaneously:

• Add another method in metadata/mod.rs called disown_device. Have this method call the StaticHeader::wipe method directly.

• Move BDA::wipe into the StaticHeader implementation.

• Update calls to BDA::wipe so that they instead call disown_device wherever necessary (or StaticHeader::wipe if they are metadata internal testing code).

Note that, after this, all StaticHeader-specific methods should have been moved into the StaticHeader implementation. So in the next step it should be possible to move the entire implementation into a separate module, one of the main parts of the goal of #1573.

[GuillaumeGomez]

Will do it in the next days then!

[mulkieran]

Great!