TSMRange - make fromTimestamp and toTimestamp interface typed instead of int

[tpoxa]

Redis documentation says:

fromTimestamp

is start timestamp for the range query (integer Unix timestamp in milliseconds) or - to denote the timestamp of the earliest sample in the time series.

So I believe with having this argument as int I can not denote - as a time of the earliest sample.
Not sure if using 0 same efficient as -

Same goes for +

[monkey92t]

It looks like this is an issue introduced by #2688, which seems to affect many APIs. However, go-redis needs to ensure API compatibility. It looks like we'll need to come up with a way to redesign it.