add CreateInAutoBatches method

[ken2403]

• Do only one thing
• Non breaking API changes
• Tested

What did this pull request do?

API implemented for this issue.

User Case Description

A method to execute Create with appropriate batch size depending on the number of fields of the struct and array size when the parameter limit is restricted.

// big array
values := [10000]{User{Name: "Smith", Age: 33, From: "Canada"}, ...}
// For SQLServer, the maximum number of parameters is 2100
err := db.CreateInAutoBatches(values, 2100).Error

[a631807682]

Similar to #6142 (comment) ,this feat can be implemented by users in their own utils.
In fact, NumField does not represent the number of parameters, gorm also supports embedded and field permissions

[ken2403]

Thanks for your comment.
I agree that this PR is overengineering, as I have tried many things and it seems that I can implement something equivalent to this by making full use of Gorm's API.

I will continue to support Gorm's simple but powerful API!
Thanks for the kind review and thank you for your time.

By the way, could you please provide a reference to embedded and field permissions?

[a631807682]

embedded

 type Author struct {
  Name  string
  Email string
}

type Blog struct {
  ID      int
  Author  Author `gorm:"embedded"`
  Upvotes int32
}

https://gorm.io/docs/models.html#Embedded-Struct
https://github.com/go-gorm/gorm/blob/master/schema/field.go#L83
field permissions

	type CustomizeFieldStruct struct {
		gorm.Model
		Name                    string
		FieldAllowCreate        string `gorm:"<-:create"`
		FieldAllowUpdate        string `gorm:"<-:update"`
		FieldAllowSave          string `gorm:"<-"`
		FieldAllowSave2         string `gorm:"<-:create,update"`
		FieldAllowSave3         string `gorm:"->:false;<-:create"`
		FieldReadonly           string `gorm:"->"`
		FieldIgnore             string `gorm:"-"`
	}

https://gorm.io/docs/models.html#Fields-Tags
https://github.com/go-gorm/gorm/blob/master/schema/field.go#L62