Mixed usage of ngql and cypher statements

[jievince]

Please check the FAQ documentation before raising an issue

Describe the bug (required)

#3506 forbids the mixed usage of ngql and cypher statements, but it forgets to handle the standalone return statement.
See the following example:

go from "Tony Parker" over like yield id($$) as vid | return $-.vid

This query should report a syntax error according to our previous design, but in fact, this query can be executed successfully before because a standalone return statement is treated as a YieldSentence in our implementation. So a standalone statement is actually a ngql statement not a cypher statement in our implementation. This strange implementation causes a bug #5113.

Pr #5116 forbids the mixed usage of ngql and return statement, but it causes incompatibility issues. After a discussion with @MuYiYong @HarrisChu , we decided to be consistent with previous behaviors.

Your Environments (required)

• OS: uname -a
• Compiler: g++ --version or clang++ --version
• CPU: lscpu
• Commit id (e.g. a3ffc7d8)

How To Reproduce(required)

Steps to reproduce the behavior:

1. Step 1
2. Step 2
3. Step 3

Expected behavior

Additional context

[xtcyclist]

Close, since an conclusion has been reached.