Copy Into Materialization Documentation and Feature Additions

[Stevedow99]

This PR has a few additions and one change:

• Changes:

  • Added a config to the copy into materialization to handle ON_ERROR in the Snowflake COPY_INTO command
    • The behavior for the config is the following:
      • if a copy_into_on_error configuration is set in a model like 'skip_file' or 'abort_statement', it will be added into the ON_ERROR clause in the copy into statement, when the given model is run
      • if no copy_into_on_error configuration is set, it will run the copy into statement without a ON_ERROR clause
      • See file dbt/models/demos/snowflake_copy_into/copy_into_demo.sql for an example of using this configuration in a model

• Additions - Documentation Changes Only:

  • The file dbt/models/demos/snowflake_copy_into/documentation/copy_into_instructions.md is detailed markdown document on how to use the copy into materialization
  • The file dbt/models/demos/snowflake_copy_into/copy_into_demo.sql serves as a referenced example in the markdown file on how to configure a model using the copy into materialization
  • The file dbt/models/demos/snowflake_copy_into/copy_into_demo_src.yml also serves as a referenced example in the markdown file on how to configure a source yaml file for an external stage when using the copy into materialization
  • The following files are pictures used in the documentation:
    • dbt/models/demos/snowflake_copy_into/documentation/doc_pics/Untitled.png
    • dbt/models/demos/snowflake_copy_into/documentation/doc_pics/Untitled 1.png
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    • dbt/models/demos/snowflake_copy_into/documentation/doc_pics/Untitled 4.png
    • dbt/models/demos/snowflake_copy_into/documentation/doc_pics/Untitled 5.png
    • dbt/models/demos/snowflake_copy_into/documentation/doc_pics/Untitled 6.png
    • dbt/models/demos/snowflake_copy_into/documentation/doc_pics/Untitled 7.png