Runtime : Snowflake connector for clickhouse

[k-anshul]

Sample model:

refresh:
  cron: "0 * * * *"

type: model
connector: snowflake
sql: >
  select * 
  from SNOWFLAKE_SAMPLE_DATA.TPCH_SF1.CUSTOMER 
  {{ if incremental }} WHERE C_CUSTKEY > '{{ .state.max_c_custkey }}' {{ end }}
  order by c_custkey asc 
  limit 1001

incremental: true
state:
  sql: SELECT MAX(C_CUSTKEY) as max_c_custkey FROM model


stage:
  connector: s3
  path: s3://<bucket>/snow

output:
  connector: clickhouse
  incremental_strategy: append
  materialize: true
  

closes https://github.com/rilldata/rill-private-issues/issues/480

[k-anshul]

closes https://github.com/rilldata/rill-private-issues/issues/480