Remove custom support for bash snippets

[andreibancioiu]

Rust-based contract interaction snippets will arise soon.

Writing contract interaction snippets in bash is now discouraged. We've dropped support for invoking such interaction snippets directly from the VSCode extension UI.

Existing bash-based interaction snippets can still be invoked from the CLI, as follows (example for the adder contract):

export PROJECT=$(pwd)
export USERS=~/multiversx-sdk/testwallets/latest/users

source interactions/testnet.snippets.sh && deploy
source interactions/testnet.snippets.sh && add