[BUG]: Pie chart UI issues

[pratibhapandey16]

What is the bug?

1. There is a huge space at the top of legends section in chart
2. Values of the pie chart are getting overlapped
3. Mode option for Pie chart has dropdown which has the fields as options
4. Title over each pie chart with metric sheet was missing

How can one reproduce the bug?
Steps to reproduce the behavior:

1. Go to Observability/Event Analytics/Explorer page
2. Enter the query in PPL query section and select 'Year to date' option from calendar and click on 'Refresh'
3. Navigate to Visualizations page
4. Select Pie chart from chart dropdown
5. Observe the issue

What is the expected behavior?

1. There should be a decent space at the top of the legend section
2. Values should not overlap and there should be little space between two pie charts
3. Mode option for Pie chart should have buttons(Pie and Donut)
4. Title over each pie chart with metric sheet should be present for better clarity between multiple pie charts

Do you have any screenshots?

@anirudha @mengweieric
cc: @abasatwar @spattnaik