[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

• [x] I have read the contributing guide and understand what's expected of me
• [x] I have run this code in development and it appears to resolve the stated issue
• [x] This PR includes tests, or tests are not required/relevant for this PR
• [x] 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

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