[Microbatch] Leverage static partitioning in dbt-bigquery materialization strategy

[borjavb]

resolves #538
docs dbt-labs/docs.getdbt.com/#

Problem

By using static partitions we are avoiding the extra steps of having to create tmp tables and then merging. Instead we use just one MERGE step.

Solution

Went through the jinja route to create the interval of partitions. Another option could have been using the generate the list of dates through GENERATE_TIMESTAMP_ARRAY (for 'hour' batch_size) or GENERATE_DATE_ARRAY (for all others)

Checklist

• I have read the contributing guide and understand what's expected of me
• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• This PR has no interface changes (e.g. macros, cli, logs, json artifacts, config files, adapter interface, etc) or this PR has already received feedback and approval from Product or DX