[Refactor] Management of store data

[jmoreira-valory]

Management of data in store is currently very cumbersome and error-prone. It is currently managed through the methods try_read_storage and create_storage, which need to be called/managed in a tighly-coupled and convoluted way.

Instead, a more manageable and mantainable method is propoded here using a single method called at the begining of the script (we consider variables not required in individual files are stored in .env file, similar to #106 ):

read_storage() {
   if $store folder don't exist -> create folder
   if $store/README.txt don't exist -> create $store/README.txt; fill README.txt
   if $store/.env don't exist -> create $store/.env

   unset RPC
   unset USE_STAKING
   unset AGENT_ID
   source $store/.env

   if variable RPC don't defined -> ask_user_rpc; store RPC on $store/.env
   if variable USE_STAKING don't defined -> ask_user_use_staking; store USE_STAKING on $store/.env
   if variable AGENT_ID not defined -> populate AGENT_ID accordingly

   # From this point on, we also need the autonomy commands.
   if /trader folder don't exist -> clone trader repository, initialize poetry, etc. 

   if $store/keys.json don't exist -> autonomy create keys.json
   if $store/agent_address.txt don't exist -> create agent_address.txt from keys.json (we have a method to do it. do we need this file?)
   if $store/agent_pkey.txt don't exist -> create agent_pkey.txt from keys.json (we have a method)

   if $store/operator_keys.json don't exist -> autonomy create operator_keys.json
   if $store/operator_address.txt don't exist -> create operator_address.txt from operator_keys.json (do we need this file?)
   if $store/operator_pkey.txt don't exist -> create operator_pkey.txt from keys.json (we have a method)

   # Files available_tools_store.json, policy_store.json, possibly not need to initialize here?
   # Files service.id.txt and service_safe_address.txt, possibly not need to initialize here? Store in the .env file instead.
}