fix: flight examples

[codonnell]

Which issue does this PR close?

Closes https://github.com/apache/arrow-datafusion/issues/9334.

Rationale for this change

It allows the arrow flight examples to compile and makes all nested examples runnable.

What changes are included in this PR?

This PR downgrades the tonic dependency to 0.10 to match arrow-flight and adds explicit [[example]] blocks so nested examples can be run with cargo run --example.

Are these changes tested?

I verified locally that the arrow flight examples compile with this change, and I was able to run queries with JDBC against the arrow_flight_sql example.

Are there any user-facing changes?

No, just example fixes.