fix unary expressions.

[yu-shipit]

1. support queries with multiple unary sign such as -+--foo
2. fix rhs scalar unary expression. Basically, the right plan for this case should be ScalarBinaryOperationExec instead of BinaryJoinExec.

Pull Request checklist

• The commit(s) message(s) follows the contribution guidelines ?
• Tests for the changes have been added (for bug fixes / features) ?
• Docs have been added / updated (for bug fixes / features) ?

Current behavior : (link exiting issues here : https://help.github.com/articles/basic-writing-and-formatting-syntax/#referencing-issues-and-pull-requests)

1. do not handle RHS unary expression properly.
2. do not support multiple unary expressions.

New behavior :
can handle queries like foo > -1
support queries with multiple unary signs like ---foo > -+-1

BREAKING CHANGES

If this PR contains a breaking change, please describe the impact and migration
path for existing applications.
If not please remove this section.

Breaking changes may include:

• Any schema changes to any Cassandra tables
• The serialized format for Dataset and Column (see .toString methods)
• Over the wire formats for Akka messages / case classes
• Changes to the HTTP public API
• Changes to query parsing / PromQL parsing

Other information:

[alextheimer]

Approved -- please see the comments for a couple questions/test-suggestions.

[alextheimer]

Thanks for the updates @yu-shipit 🙏