Dark theme color and styles are not proper

[RaghavendranC-Eaton]

          I will just spill out every single thing I noticed. Many of these might be out of scope; feel free to defer for future improvements (or just sit on it and wait for ng16, material design 3)

1. Progress Bar

Dark theme only. Accent color is using 200 colors, unlike the default and primary.

2. Sliders

Same issue

3. Bottom sheet

Probably not an issue. I just noticed the bottom sheet is still LTR in a RTL setting

4. FAB

Perfectionist moment! The icon is not vertically centered with a 0.86px vertical offset. This applies to all variants and both FAB components (regular FABs and mini FABs)

5. Text Field

Applies to both light and dark theme:

6. Text Field (2)

Dark theme only:

Originally posted by @huayunh in #188 (comment)