Switch cli::sql to the new API

[rushmorem]

What is the motivation?

We recently introduced a new API for surrealdb. This is the first commit in a series of commits to update the server to use the that API.

What does this change do?

It updates the cli::sql module to the new API.

One positive side-effect of this is that it is now possible to use the REPL without having to spin up a server first. This is because the connection string now allows using any database engine supported by SurrealDB. That includes the embedded ones. This means that one can now run

surreal sql --conn mem:// --ns test --db test

or just

surreal sql --conn mem://

which will embedded an in-memory database and run queries against that.

Another positive side effect is that the REPL now fully supports LET and USE statements regardless of the database engine you are using.

What is your testing strategy?

I ran

cargo run --no-default-features -F storage-mem -- sql --conn mem:// --ns test --db test

and tested running some queries.

Is this related to any issues?

• It fixes Feature: Remember previously specified NS and DB in command-line REPL #35
• It fixes Bug: LET statement variables do not stay across queries in the CLI REPL #39
• It fixes Bug: Can't define parameters #1258

Have you read the Contributing Guidelines?

• I have read the Contributing Guidelines