fix(general): use alloy namespace imports and flatten example directories

[zerosnacks]

• Replaces the individual direct crate imports with the alloy namespace one
• Creates a flat directory structure, no more multi-crates

[mattsse]

hmm, I'm not sure we should do this,

I kinda like having individual crates for examples,
because some examples are a bit larger and include sol source files etc.

[zerosnacks]

hmm, I'm not sure we should do this,

I kinda like having individual crates for examples, because some examples are a bit larger and include sol source files etc.

Personally I don't really mind the multi-crate architecture, this is a proposed solution to the request of @gakonst to get out of the multi-crate setup.

I was imagining a shared assets directory to enable easy re-use of assets (artifacts, contracts, etc..) across examples.

I think the issue of crates being difficult to navigate to will be resolved by linking them in the README and it being a one-click to any example.

That said, in practice I don't expect anyone to actually import these examples as crates in their codebase - favouring this flat directory setup.

[zerosnacks]

Replaced by PR only covering switch to Alloy namespace: #11