Support dbt 1.0

[courentin]

Hello, dbt-core 1.0 has been rolled out and I'd to make this adapter compatible.

I'm starting this issue to document what should be done for v1 readiness. Do not hesitate to comment, I can update this issue.

• Use dbt event module see https://github.com/dbt-labs/dbt-core/blob/HEAD/core/dbt/events/README.md#adapter-maintainers
• Fix on_schema_change is not available despite supporting 0.21.0 #47
• Create a profile_template.yml see https://docs.getdbt.com/reference/commands/init#profile_templateyml
• Pin minor dbt-core versions instead of fix see https://blog.getdbt.com/getting-ready-for-v1-0/#why-we-care-about-version-numbers-and-why-you-should-too-
• Restructure the macros directory see Reorganize global project (macros) dbt-labs/dbt-core#4154

I'm wondering if we should create a branch v1.0 to ease testing?