rust frontend: bind & plan project

[xiangjinwu]

explain select v2 from t

Note there exist 2 alternatives:

• Plan a scan with all columns + a project picking the referenced columns, then rely on optimizer to simplify the scan. This is how the java frontend is working now.
• Track all referenced columns in binding phase, and plan a scan with only those columns directly.

[neverchanje]

To fully accomplish the support of proj, there are still some todos remained:

• Support wildcard (star *)
• Support AS alias on select item.