Support from_days/to_days in TiFlash

[LittleFall]

pingcap/tiflash#4678

Feature Request

Is your feature request related to a problem? Please describe:

Describe the feature you'd like:

Support from_days in TiFlash
MySQL doc:
https://dev.mysql.com/doc/refman/8.0/en/date-and-time-functions.html#function_from-days
TiDB implementation:

tidb/expression/builtin_time.go

Line 887 in 5889d4c

func (b *builtinFromDaysSig) evalTime(row chunk.Row) (types.Time, bool, error) {

Support to_days in TiFlash
MySQL doc:
https://dev.mysql.com/doc/refman/8.0/en/date-and-time-functions.html#function_to-days
TiDB implementation:

tidb/expression/builtin_time.go

Line 7027 in 5889d4c

func (b *builtinToDaysSig) evalInt(row chunk.Row) (int64, bool, error) {

Describe alternatives you've considered:

Teachability, Documentation, Adoption, Migration Strategy: