Preliminary compound datatype support

[mtoy-googly-moogly]

All that refactoring leads to this ... arrays and records working in more places. Using the word "compound" data for this, saving the word "composite" for cube-like sources.

The WN for this is https://github.com/malloydata/whatsnext/blob/main/wns/WN-0015-arrays-and-records/WN-0015.md but this is an MVP level first step. The MVP is based on avoiding some of the most common reasons Meta users are having to drop into SQL when working with compound data

• Can select: a compound computation
• Can pass a compound computation to a function call
• Literals exist for compound types
• Some array functions in the standard, or presto library

• A query can select an array or an expression that has an array type
• There is an array literal
• You can pass arrays to functions
• There is a record literal
• A record can be selected
• A literal for an array of records
• An array of records can be selected
• Record in a source
• Array in a source
• Array of records in a source
• Tested in all dialects
• Maybe add split/join/contains for @lloydtabb
• Merge some doc for record and array datatypes malloydata.github.io#202
• Add tests for group_by: records and arrays

[mtoy-googly-moogly]

Thanks @lloydtabb for the test templates for the grouping ...

      test('can build rec select with data from table', async () => {
        await expect(`
          # test.debug
          run: ${conName}.table('malloytest.state_facts') -> {
            select: airport_count, val is {airport_count}
            order_by: airport_count desc
            limit: 10
        }
        `).malloyResultMatches(runtime, {
          'airport_count': 1845,
          'val.airport_count': 1845,
        });
      });

      test('can build record group with data from table', async () => {
        await expect(`
          # test.debug
          run: ${conName}.table('malloytest.state_facts') -> {
            group_by: airport_count, val is {airport_count}
            order_by: airport_count desc
            limit: 10
        }
        `).malloyResultMatches(runtime, {airport_count: 1845});
      });

      test('can build array group with data from table', async () => {
        await expect(`
          # test.debug
          run: ${conName}.table('malloytest.state_facts') -> {
            group_by: airport_count, val is [airport_count]
            order_by: airport_count desc
            limit: 10
        }
        `).malloyResultMatches(runtime, {airport_count: 1845});
      });