chore(core/raw): align info method of kv::Adapter and typed_kv::Adapter

[koushiro]

Which issue does this PR close?

No

Rationale for this change

The metadata method of kv::Adapter and info method of typed_kv::Adapter is misaligned.

What changes are included in this PR?

• rename metadata method of kv::Adapter: fn metadata(&self) -> Metadata; => fn info(&self) -> Info;
• rename Metadata type of kv module: pub struct Metadata {...} => pub struct Info {...}
• remove impl From<kv::Metadata> for AccessorInfo { ... }

Are there any user-facing changes?

• rename kv::Adapter::metadata() => kv::Adapter::info()
• rename kv::Metadata => kv::Info
• remove impl From<kv::Metadata> for AccessorInfo { ... }

[Xuanwo]

Thank you @koushiro for polishing our code!

[Xuanwo]

Hi, @koushiro, there are some conflicts preventing us from merging this PR. Could you take a look?