feat: Adds date_part function tests

[devanbenz]

Adds tests for date_part to ensure that we can support it using influxql

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specs for date_part

date_part(part, expression)

Arguments

- part: Part of the date to return. The following date parts are supported:
   - year
    - quarter (emits value in inclusive range [1, 4] based on which quartile of the year the date is in)
    - month
    - week (week of the year)
    - day (day of the month)
    - hour
    - minute
    - second
    - millisecond
    - microsecond
    - nanosecond
    - dow (day of the week where Sunday is 0)
    - doy (day of the year)
    - epoch (seconds since Unix epoch)
    - isodow (day of the week where Monday is 0)
- expression: Time expression to operate on. Can be a constant, column, or function.

Example usage:

SELECT * FROM some_measurement
WHERE time >= now() - 10d AND time <= now() AND (date_part(time, dow) != 0 AND date_part(time, dow) != 6)

[davidby-influx]

LGTM. Are you going to merge this before the rest of the work is done? Would it be better to merge this after the implementation is complete?

Please add a reviewer from the V3 InfluxQL team, as well.

[devanbenz]

LGTM. Are you going to merge this before the rest of the work is done? Would it be better to merge this after the implementation is complete?

Please add a reviewer from the V3 InfluxQL team, as well.

Since I don't need to add any functionality outside of tests I will merge this and the influxdb changes at the same time.

[mhilton]

Are you planning to support the uppercase versions of the parts too? Eg 'YEAR' 'DOW'? If so do you want to have some tests for those too?