Create txn stream crate in this repo

[rtso]

Description

Clean up transaction_stream.rs' (renamed from grpc_stream.rs`) so we can make a crate of it, which will be used in the SDK.

TransactionStream

transaction_stream.rs defines a struct TransactionStream that has these methods:

• init_stream establishes a connection with the grpc stream
• get_next_transaction_batch fetches the next transaction response from grpc
• is_end_of_stream signals if you've reached the end of the stream
• reconnect_to_grpc will attempt to reconnect with grpc if there's an error with the stream
• reconnect_to_grpc_with_retries is a wrapper around reconnect_to_grpc that adds retry logic

How processors use TransactionStream

In worker.rs, fetch_transactions_from_transaction_stream will initialize and manage the TransactionStream, filtering transactions, sending the transactions to channel, handle reconnection if necessary.

Testing

cargo run --release -- -c config.yaml
with and without starting_version set

[rtso]

Need to add this to this repo to avoid circular dep. Addressed all the comments in aptos-labs/aptos-indexer-processors#397