Avoid showing too many entries in the pie chart once.
Avoid showing too many entries in the pie chart once.

When there are too many data entries, the pie chart is too crowded to
view. So we set a parameter in the class EchartsData called
maximumEntries, only the top <maximumEntries> will be shown and the rest
will be added to a single entry called 'other'.

Test: mannual tested.
Change-Id: I84bfadd3513c5827426d84ee7d5ad957b1ac5eab

google/ota-analyzer,google/ota-analyzer,google/ota-analyzer