[FE] UI changes to the QB for new metric

[perivamsi]

These are all label/text changes to the query builder when the user does New > Metric

• Add (optional) to filters
• Measure calculation instead of Summarize
• Remove the by in the breakout

These are more involved changes that need additional details from the product side and probably should be spun off as separate issues

• Primary time dimension instead of nothing in the breakout
• Add the sidebar with the instruction (this needs to be spec-ed out)

[luizarakaki]

Primary time dimension instead of nothing in the breakout

This requires new design input, as now it is possible to add multiple non-time dimensions there