Update RFS from ~8.0 to ~9.0 for Vartheme BS4 and VARTHEME_BS4_SUBTHEME

Problem/Motivation

RFS ~8.0 dose not have responsive padding and margin.
#3170682: Convert to use REM and EM instead of PX
RFS ~9.0 has responsive padding and margin.
to be able

  +font-size(4rem)

  // The font-size mixin is a shorthand which calls
  // +rfs(4rem, font-size)

  // Other shorthand mixins that are available are:
  // +padding(4rem)
  // +padding-top(4rem)
  // +padding-right(4rem)
  // +padding-bottom(4rem)
  // +padding-left(4rem)
  // +margin(4rem)
  // +margin-top(4rem)
  // +margin-right(4rem)
  // +margin-bottom(4rem)
  // +margin-left(4rem)

  // For properties which do not have a shorthand, the property can be passed:
  // +rfs(4rem, border-radius)

  // Whenever a value contains a comma, it should be escaped with `#{}`:
  // +rfs(0 0 4rem red #{","} 0 0 5rem blue, box-shadow)

Proposed resolution

Upgrade RFS from ~8.0 to ~9.0
https://github.com/twbs/rfs#input

Remaining tasks

• Upgrade RFS
• Change padding and margin to RFS
• Test
• Release

User interface changes

Responsive padding and margin

API changes

N/A

Data model changes

N/A