[Feature] Support aggregate function FIRST

[yukkit]

Is your feature request related to a problem? Please describe.
Returns the field value with the oldest timestamp.

Describe the solution you'd like

• Syntax

--- Returns the oldest colume value (determined by timestamp) associated with the colume name.
FIRST(<time colume>, <colume name>): <colume value>

• arguments

time colume: ......
colume name: Any fields or tags

• returns

colume value: the oldest colume value, The data type is consistent with the specified column

Describe alternatives you've considered

Add to the https://github.com/cnosdb/cnosdb/tree/main/query_server/query/src/extension/expr/aggregate_function

Additional context

The mainstream database supports FIRST show below:

timescaledb
https://docs.timescale.com/api/latest/hyperfunctions/first/

InfluxDB
https://docs.influxdata.com/enterprise_influxdb/v1.9/query_language/functions/#first