Extend SessionBuilder trait to operate on SessionState and SessionContext

[gabotechs]

While integrating TPCH benchmarks with the codebase, I realize that the SessionBuilder trait needs to allow more flexibility to users for configuring their session.

In order to understand what's needed, it's convenient to know how users create DataFusion sessions:

1. They create their SessionStateBuilder, and start building their session. ✅ we allow configuring this
2. They call .build() and get a SessionState, which can be further configured. ❌ we don't allow configuring this
3. They create a new SessionContext out of the state, which can be further configured. ❌ we don't allow configuring this

This PR adds two more methods to the SessionBuilder trait, and it now looks like this:

pub trait SessionBuilder {
    fn session_state_builder(&self, builder: SessionStateBuilder) -> Result<SessionStateBuilder, DataFusionError>;
    async fn session_state(&self, state: SessionState) -> Result<SessionState, DataFusionError>;
    async fn session_context(&self, ctx: SessionContext) -> Result<SessionContext, DataFusionError>;
}

This allows the user to configure:

1. SessionStateBuilder ✅
2. SessionState ✅
3. SessionContext ✅

This unlocks wiring up the datafusion-distributed project with the TPCH benchmarks from #73