[Feature]: Support any time averaged snapshot

[chengzhuzhang]

Is your feature request related to a problem?

When comparing two datasets in e3sm_diags core sets, the basic idea is two compare two ANN/seasonal/monthly mean snapshot. For support arbitrary time averaged data, currently, we can only hack it by renaming the time snapshot file with supported seasons valueseasons = ["ANN", "01", "02", "03", "04", "05", "06", "07", "08", "09", "10", "11", "12", "DJF", "MAM", "JJA", "SON"]. The new feature should make it flexible to pick up files (follows a set file name convention), and generate viewers with correct custom seasons (with according time range).

Describe the solution you'd like

No response

Describe alternatives you've considered

No response

Additional context

See comment here: #652 (comment)