Add HeightIndex interface to database

[DracoLi]

Why this should be merged

Add an BlockDatabase interface to database package. This will be used by the VMs to integrate x/blockdb, starting with coreth (see POC PR).

How this works

Interface added to database/database.go

How this was tested

Need to be documented in RELEASES.md?

No

[Copilot]

Pull Request Overview

This PR adds a new BlockDatabase interface to the database package to provide a standardized API for blockchain block storage and retrieval operations. This interface will enable VM integration with the x/blockdb component.

• Introduces BlockDatabase interface with methods for block CRUD operations
• Adds inspection and resource management capabilities to the interface

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[maru-ava]

Does this have a target consumer (i.e. simplex)?

[DracoLi]

@maru-ava yes, coreth will be using this first. I'm working on a PR to switch it to use blockdb.

[maru-ava]

@maru-ava yes, coreth will be using this first. I'm working on a PR to switch it to use blockdb.

Maybe link the coreth PR that depends on this PR so that the intention is clear?