Add AttributeType validation in text-related operator executors

[aahei]

During the review of PR #1924, we found that the following operators require the input attributes to be of certain types, but currently do not have constraints in the code in the back-end.

These operators only take string-type input attributes, but do not check the type in the backend:

• Regular Expression
• Dictionary Matcher
• Keyword Search
• Sentiment Analysis
• Unnest String
• HTML Visualizer
• Word Cloud

Additionally, the Linear Regression operator only takes numeric type input attributes but does not check the type.

For the Hash Join and Interval Join operators, we may consider whether enforcing the check for the equality of left and right attribute types.

[sadeemsaleh]

@aahei I suggest, before we do the change for the HTML visualizer is to do a test using some existing use cases. I observed most cases pass type ANY from Python UDF to the HTML visualizer, not sure though why users choose ANY instead of String.

[Yicong-Huang]

Just a side note regarding the ANY, it is a general type that represents all types for the engine to work. In #1957 we are considering removing it from the UI so that users won't select it.