Remove ink-as-dependency

[HCastano]

As part of the ink! RC7 release the ink! codegen started generating a ContractRef
struct alongside the Contract struct. Since then there has been no need for
ink-as-dependency because all contracts get a generated Ref struct which can be used
anywhere ink-as-dependency would've been used.

The release notes even mention that the Ref struct was meant to be the successor to the
ink-as-dependency concept.

MyContractRef is pretty much the same of what we had gotten with the old
ink-as-dependency. It is a typed thin-wrapper around an AccountId that is mirroring the
ink! smart contract's API and implemented traits.

This PR removes ink-as-dependency since it is no longer needed.

[HCastano]

I'll fix the CI tomorrow 😔

[xgreenx]

You can't just remove the ink-as-dependency feature because it is still used to prevent multiple call, deploy, and __ink_generate_metadata.

@Robbepop mentioned in that #665 the idea with in-as-root feature. All no mangle methods can be marked with that feature and cargo-contract can enable it during compilation.

[HCastano]

You can't just remove the ink-as-dependency feature because it is still used to prevent multiple call, deploy, and __ink_generate_metadata.

@Robbepop mentioned in that #665 the idea with in-as-root feature. All no mangle methods can be marked with that feature and cargo-contract can enable it during compilation.

Hmm yeah, I figured the ContractRef impl was a bit more clever, but you're right we
still need some way to prevent multiple of those no_mangle calls.

So the main thing I really wanted to get rid of here was the
#[ink::contract(compile_as_dependency = ...)] syntax from the language.

I think we can still do that without removing the ink-as-dependency feature flag. I
don't really see a difference between that and ink-as-root, the feature will still need
to be enabled/disabled somewhere.

[xgreenx]

I think we can still do that without removing the ink-as-dependency feature flag. I
don't really see a difference between that and ink-as-root, the feature will still need
to be enabled/disabled somewhere.

ink-as-root should be enabled only for the root contract, not for subcontracts, and cargo-contract can enable it because the developer calls cargo contract build for the root contract.

ink-as-dependency should be enabled for all subcontracts, and cargo-contract can't recognize what contract is sub contract=)

[HCastano]

Okay so I'm gonna split this out into two PRs.

1. Remove compile_as_dependency
2. Replace ink-as-dependency with ink-as-root

For (1) I've opened #1168, and for (2) I've started playing around with something today, will
maybe open a PR tomorrow.