feat(sqlserver): Part 3 — plain SQL auth, TLS params, QUOTED_IDENTIFIER init

[axellpadilla]

Part of dbt-labs#15714 (upstream feature request). Depends on #2.

Most of crates/dbt-auth/src/sqlserver/ already exists and is unit-tested (Entra flows). This part is additive, not a rewrite.

Work items

• Add plain SQL auth (SQLServerAuthIR variant + parse_auth branch, maps straight to URI userinfo like v1's ADBC backend does)
• Fill in apply_connection_args TODOs — encrypt, TrustServerCertificate, connection timeout — porting values/defaults directly from dbt-sqlserver/dbt/adapters/sqlserver/sqlserver_backend.py:367-401 (same driver, already solved there)
• src/init.rs — SET QUOTED_IDENTIFIER ON connection-init SQL (required, not optional — consequence of the Part 1 quoting decision)
• Unit tests alongside existing ones in sqlserver/mod.rs

Full detail: dbt-sqlserver-v2-roadmap plan/02-implementation-steps.md §5.4

PRs against sqlserver-v2-port in this repo, use Closes #<this issue>.