feat: add schema for tpcds queries

[richtia]

Adding the schema for TPC-DS queries

[CLAassistant]

All committers have signed the CLA.

[jacques-n]

@richtia , any chance you want to also add at least a smoke test that uses this? It seems lonely right now.

[JamesRTaylor]

@richtia - thanks for the PR. Here's some feedback:

• I like the idea of documenting the tpcds schema and being consistent with the tpch convention in terms of the location of the schema file. We actually use Calcite to define the tpch and tpcds schema, but having this documented is definitely useful too.
• Remove the duplicate definition of this schema here.
• Modify the test here that uses keyconstraints_schema.sql to use your new schema instead, and rename the test file to TpcdsSchemaTest.java