New lint: pub trait method default implementation removed

[SmolSir]

When the pub trait method's default implementation is removed, the method is no more provided and turns into a declared method. This forces the new version to implement the now-declared method in all of the impl blocks which were deriving that trait with its previously-provided method in the old version.

Required new version: Major

This requires some schema additions:

• adding the edge from Trait to its Methods [linked PR]
• enabling the has_body field for Method [linked PR]

[obi1kenobi]

Accidental duplicate of #294.