allow to specify min_group_size in graphs that include grouping (e.g. using 'color', 'facet_row/col' etc.)

when using 'grouped' plots, we'd often like to see trends/differentations between separate groups.
however, it is common that some of the groups are very 'small', thus the data shown for them is confusing (and sometunes also distorts the rest of the plot, because the range can be very large).

i think allowing specification of min_group_size (Optional[int]) can be very beneficial, mitigating this issue, and eliminating the need of boilerplate code from the user side.

thank you for all your great work!

首先追蹤支援 color、facet_row 和 facet_col 的分組繪圖路徑，然後檢查其現有測試與分組行為。定義 Optional[int] min_group_size 應如何套用於這些分組選項，包括無效值或省略值。完成的標準是：小型群組能一致地被排除，而不需要使用者自行篩選，並且涵蓋受支援的分組情境。