fix: move Soldeer dependencies

[Serial-ATA]

Overview

• As far as I can tell, Soldeer will always put the dependencies in the root. I moved foundry.toml into contracts/ to fix that.
• I had to manually add append /src to the tnt-core remapping
• Remove submodules from Dependabot
• Fixed import in HelloBlueprint.sol (Soldeer keeps versions in the path)

[shekohex]

1. We need to keep the foundry.toml in the root path, otherwise you cannot run foundry build/test from the root, and you have to path --root ./contracts everywhere to get it to work.
2. The remappings.txt should be kept outside of the config; most of the Solidity LSP reads this file, so we need to keep it separate.
3. No need to use versioning in the imports, it's not the idiom in Solidity, instead we put tnt-core/=dependencies/tnt-core-0.1.0/src/ or something like that in the remapping.txt
   Soldeer does not (by default) update the remapping there is a flag for that afaik, and we don't need it for now.

[shekohex]

Just small change, otherwise looks good!