feat(jinja): add b64decode/b64encode builtin filters #3869

Job	Run time
changes	6s
test-dbt-versions (1.5)	1m 29s
test-dbt-versions (1.6)	1m 41s
test-dbt-versions (1.3)	1m 52s
test-dbt-versions (1.9)	1m 43s
test-dbt-versions (1.10)	1m 51s
test-dbt-versions (1.4)	1m 31s
test-dbt-versions (1.7)	1m 28s
test-dbt-versions (1.8)	1m 46s
test-vscode-e2e	0s
test-vscode	0s
doc-tests	34s
cicd-tests-windows	11m 50s
migration-test	1m 39s
style-and-cicd-tests (3.12)	24m 24s
style-and-cicd-tests (3.13)	24m 34s
style-and-cicd-tests (3.11)	23m 38s
style-and-cicd-tests (3.10)	23m 51s
engine-tests-docker (postgres)	2m 14s
engine-tests-docker (spark)	5m 33s
engine-tests-docker (duckdb)	1m 45s
style-and-cicd-tests (3.9)	23m 53s
engine-tests-docker (risingwave)	2m 40s
engine-tests-docker (trino)	7m 58s
engine-tests-docker (mysql)	1m 47s
engine-tests-docker (starrocks)	2m 30s
engine-tests-docker (mssql)	1m 53s
engine-tests-docker (clickhouse)	2m 55s
ui-style	0s
ui-test	0s
engine-tests-cloud	0s
	2h 57m 5s

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