Resolved issue of dark icons not visible in bottom NavBar and Achievement Fragments, in dark mode

[ShashwatKedia]

Description (required)

This PR resolves the issue of visibility of black/dark blue coloured icons in the bottom navigation bar and in the achievements fragment.

Fixes #5194

What changes did you make and why?

1. For the info icon in the Achievements fragment, I changed the colour-tint of icons to primaryLightColour
2. For the BottomNavbar icons, I changed the 'color_state_nav_tab_dark' to primaryLightColour
3. Additionally, I noticed that the floating button's plus sign was not aligned with the UI guidelines for dark mode, so I added a tint colour to it

Tests performed (required)

Tested betaDebug on OnePlus Nord CE 2 Lite with API level 31.

Screenshots (for UI changes only)

[nicolas-raoul]

Looks great! Would you mind posting screenshots showing light mode too?

[ShashwatKedia]

Sure! There you go!

[ShashwatKedia]

@nicolas-raoul Sorry to disturb you, but if everything is okay, kindly merge the PR :)

[nicolas-raoul]

It looks great now, thanks and sorry for the delay! :-)

[ShashwatKedia]

No issues, thanks for the merge!!