DBT-747: Stop support for views materialization in dbt-impala

[vamshikolanu]

Describe your changes

Currently, there is no easy way to differentiate between tables and views in impala. The current query for list_relations_without_caching is not optimized; hence it started failing for larger number of tables.

Internal Jira ticket number or external issue link:

https://jira.cloudera.com/browse/DBT-747

Testing procedure/screenshots(if appropriate):

https://gist.github.com/vamshikolanu/e77a968cc7a9631390c2ed6f957f60c4

Checklist before requesting a review

• I have performed a self-review of my code
• I have formatted my added/modified code to follow pep-8 standards
• I have checked suggestions from python linter to make sure code is of good quality.

[amaralvieira]

I can only say that support for view materialization is a must. Removing it would only make this adapter unusable. 🙁

[kennycontreras]

Would it be better to implement a new argument/feature to skip the macro if needed instead of removing the whole code for the get_relation_type macro?
I agree with @amaralvieira