refactor: Hide lifetimes from external crates, support error cloning

[BrianBland]

Improve usability of TrieDB as a crate by making the following external-facing changes:

• Remove lifetimes from Transactions, by instead holding an Arc of a database handle
• Allow error types to be clonable

This re-introduces DatabaseInner, with Database simply holding an Arc of the inner struct.

Replaces #108

[cb-heimdall]

🟡 Heimdall Review Status

Requirement	Status	More Info
Reviews	🟡 0/1	Denominator calculation Show calculation 1 if user is bot 0 1 if user is external 0 2 if repo is sensitive 0 From .codeflow.yml 1 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 1 1 1 if commit is unverified 0 Sum 1

[and-cb]

It's very rare for errors to implement Clone, which is why most errors (in the std lib too) don't implement it. Is there a specific reason why we want them here? The PR description mentions "usability reasons", but I struggle to find places where errors are cloned instead of being simply propagated.

[BrianBland]

This was introduced for seamless compatibility with Reth, as they appear to clone errors. I'll double check whether or not this is truly necessary

[BrianBland]

Upon further review this mostly stems from Reth cloning Results (example) including the ProviderError

We don't really need to embed the raw TrieDB Error inside of the ProviderError, and can instead just stringify this to remove the need for error cloning.

[and-cb]

Instead of rewriting all the code to use self.inner. instead of self., I would suggest simply changing impl Database to impl DatabaseInner. The only methods that need to stay inside impl Database are the constructors (create and new). Everything else can be transparently delegated by Deref

[BrianBland]

I believe this would require making DatabaseInner public, which we probably want to avoid

[BrianBland]

Another option might be to make Transaction accept a generic DB which implements Deref<Database>, so that we can use &Database or Arc<Database> as needed.