[Enhancement]: counter_agg() support for 64bit numeric types

[Xeitor]

I was looking into counter_agg() function to work with some 64bit SNMP counters.

the current function the signature is:
counter_agg(ts TIMESTAMPTZ,value DOUBLE PRECISION[, bounds TSTZRANGE]) RETURNS CounterSummary

since the counter are unsigned 64bit integers I wanted to use Postgres's Arbitrary Precision Numbers: NUMERIC(precision, scale) with precision: 20 and scale: 0.

would it be possible to add support for this numeric type in counter_agg()?

from the docs:

timescaledb-toolkit/docs/counter_agg.md

Line 163 in 69278f1

##### ¹ Note that the `value` is currently only accepted as a `DOUBLE PRECISION` number as most people use that for counters, even though other numeric types (ie `BIGINT`) might sometimes be more intuitive. If you store a value as a different numeric type you can cast to `DOUBLE PRECISION` on input to the function.

docs say that I can cast to double precision upon function input, what will happen with very large numbers?