Normalize `date` and `time` value annotations

[Alan Cai]

I noticed that some TIME values in the test data use an annotated struct:

e.g.:

partiql-tests/partiql-tests-data/eval/query/order-by.ion

Line 43 in e24d8ef

 { 'data_value': $time::{'hour':12, 'minute':12, 'second':12.1,'timezone_hour':null.int,'timezone_minute':null.int} }, 

While some other TIME values use an annotated string:

e.g.

partiql-tests/partiql-tests-data/eval/spec-tests.ion

Lines 755 to 758 in e24d8ef

 logs: [{sensor:1, co:0.4, timestamp: $time::"04:05:06"},    // ex in spec used an undocumented timestamp 
        {sensor:1, co:0.2, timestamp: $time::"04:05:07"},    // syntax. changed to use time annotation 
        {sensor:1, co:0.5, timestamp: $time::"04:05:10"},    // in the test suite 
        {sensor:2, co:0.3} 

The partiql-tests spec proposal defines using the annotated string form: https://github.com/partiql/partiql-tests/blob/e24d8ef837303e675bc7c29b8a41f3cc81d6b96e/docs/partiql-tests-schema-proposal.md#modeling-partiql-types-in-ion.

These should likely be normalized to the same thing.

TODO:

• Also sort out the modeling of other time/timestamp types that use timezone

[Alan Cai]

date is also modeled using a timestamp in some tests

partiql-tests/partiql-tests-data/eval/query/order-by.ion

Line 48 in e24d8ef

 { 'data_value': $date::2021-08-22 }, 

The spec proposal uses an annotated string: https://github.com/partiql/partiql-tests/blob/e24d8ef837303e675bc7c29b8a41f3cc81d6b96e/docs/partiql-tests-schema-proposal.md#modeling-partiql-types-in-ion.

[Alan Cai]

Also need to normalize how PartiQL timestamps are to be represented in Ion (could be the same as Ion?)