[Microbatch] Optimizations: use view for temp relation + remove using clause during delete statement

[MichelleArk]

resolves #1228
docs dbt-labs/docs.getdbt.com/# N/A

Problem

Microbatch performance is underwhelming for dbt-snowflake! A couple underlying reasons:

1. Microbatch largely inherits from delete+insert strategy in snowflake, which has been optimized to use a temp view instead of table. However, microbatch is still using a temp table! More details: https://docs.getdbt.com/reference/resource-configs/snowflake-configs#temporary-tables

• Note that it is always safe to do so for microbatch since there is no unique_key necessary

2. The using clause is unnecessary in the microbatch delete statement, because microbatch does not require a merge key and the where clause is sufficient for a safe deletion.

Solution

1. Apply temp view optimization to microbatch. Was just a matter of extending a couple if statements that only checked for insert+delete previously
2. Remove extraneous using clause

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

[github-actions]

Thank you for your pull request! We could not find a changelog entry for this change. For details on how to document a change, see the dbt-snowflake contributing guide.

[QMalcolm]

Looks good to me!

[QMalcolm]

🚀 This is a greeeeaaaat catch! Nice!