Support MySQL 5.X as a target

[bobvawter]

These older versions of MySQL don't support CTE's, which, at a minimum, prevents the schema-inspection queries from running. There may be other unknown-unknown's in terms of SQL workload changes.

[ryanluu12345]

My understanding here is that we need to just add a new set of queries that don't use CTEs for MySQL and then drill in the version of the database throughout the codebase so that we can know when to use the MySQL 5.7 queries

[bobvawter]

Adding support in schemawatch is the first identified task.

Run TEST_TARGET_CONNECT=mysql://root:SoupOrSecret@localhost:3306/ go test ./... to validate.

[bobvawter]

Possibly an opportunity for #996

[ryanluu12345]

Yep, I see what you mean by adding support in schemwatch. I see the query templates inside of internal/target/schemawatch/dependencies.go. Based on my read, it looks like we'll just need to add a new mysql5_7 template and then update the MySQL case statement so that if we see version 5.7, we use the new query without CTEs.

[ryanluu12345]

Regarding #996, I can take a look at that once I get this base functionality working. Then can refactor this so it applies to all templates for every dialect.