Add median and median_approx for Spark engine

[nhanitvn]

Description and related tickets, documents

Reviewers: @hai-adatao @PangZhi

Breaking changes & backward compatible issues

How to test

PR Progress

Make sure all checkboxes below are checked before merged

• [x] Branch is in format prefix/description (see this)
• [x] Merge check has no conflicts. PR checks passed.
• [x] Code review is done.

[PangZhi]

retest this please

[PangZhi]

@hai-adatao ut pass. we can merge now.