Feat: add tag to skip namespace in embedded structures

[arxeiss]

Enhances

Introducing new skipns validate tag, that allows to skip the name of embedded struct, when printing invalid field namspace.

type Outer struct {
	Embedded `validate:"skipns"`
}

See #1413 for more extensive examples and discussion.

Make sure that you've checked the boxes below before you submit PR:

• Tests exist or have been written that cover this particular change.

@go-playground/validator-maintainers

Fixing #1413 and #776

[coveralls]

coverage: 73.672% (+0.02%) from 73.655%
when pulling f881394 on arxeiss:master
into 20f7df6 on go-playground:master.