fix: Set DatabricksConnectionConfig to only use a shared_connection with U2M OAuth #3843

Job	Run time
test-dbt-versions (1.6)	1m 44s
test-dbt-versions (1.5)	1m 28s
test-dbt-versions (1.3)	1m 41s
test-dbt-versions (1.4)	1m 31s
test-dbt-versions (1.7)	1m 45s
test-dbt-versions (1.10)	1m 54s
test-dbt-versions (1.9)	1m 52s
test-dbt-versions (1.8)	1m 43s
changes	9s
test-vscode	-7s
test-vscode-e2e	-10s
cicd-tests-windows	9m 8s
migration-test	1m 34s
doc-tests	37s
style-and-cicd-tests (3.12)	3m 18s
style-and-cicd-tests (3.9)	3m 9s
style-and-cicd-tests (3.10)	3m 6s
engine-tests-docker (duckdb)	1m 34s
engine-tests-docker (clickhouse)	2m 56s
engine-tests-docker (postgres)	2m 0s
engine-tests-docker (risingwave)	2m 43s
style-and-cicd-tests (3.11)	3m 4s
engine-tests-docker (mysql)	1m 48s
engine-tests-docker (spark)	4m 59s
engine-tests-docker (starrocks)	2m 54s
engine-tests-docker (trino)	8m 32s
engine-tests-docker (mssql)	1m 45s
style-and-cicd-tests (3.13)	3m 19s
ui-test	0s
ui-style	0s
engine-tests-cloud	0s
	1h 9m 56s

Provide feedback