helper/validation: add StringRuneCountBetween() and StringBytesBetween() instead StringLenBetween()

[ryodocx]

Summary

• In this PullRequest, add validator in order to count string length correctly.
• Current, StringLenBetween() count byte length.
• For example Japanese, 1 character mean 3 bytes in UTF-8.
  • Sometimes, improper validation implements in terraform-provider via this behavior

What's changes?

• add StringRuneCountBetween() for validate number of characters
• add StringBytesBetween() for validate number of bytes (it's just copy of StringLenBetween())
• StringLenBetween() is to deprecated
• add validation for parameters(min, max)
• add test

Related issues

• action.fixed_response.message_body in aws_lb_listener_rule is validated not by length, but by bytes terraform-provider-aws#19846
• ELBv2 FixedResponse with message_body (<= 1024 chars && > 1024bytes) cannot be registered  terraform-provider-aws#22949

[ryodocx]

@bflad Could you help this PR?