[LinearProgress] Make color adapt to theme type

[ahtcx]

• I have followed (at least) the PR section of the contributing guide.

I found the linear progress bars don't look amazing with a dark theme because it uses the lighten helper function, so I've made it use either lighten or darken depending on the current theme.

	Current	Proposed changes
Light
Dark

[mui-pr-bot]

Details of bundle changes.

Comparing: 45d2ce2...d2e24af

bundle	parsed diff	gzip diff	prev parsed	current parsed	prev gzip	current gzip
@material-ui/core	-0.06%	-0.01%	329,697	329,491	90,071	90,061
@material-ui/core/Paper	0.00%	-0.00%	68,774	68,774	20,486	20,485
@material-ui/core/Paper.esm	0.00%	-0.02%	62,148	62,148	19,216	19,212
@material-ui/core/Popper	-0.01%	+0.13% 🔺	28,468	28,466	10,177	10,190
@material-ui/core/Textarea	0.00%	0.00%	5,094	5,094	2,137	2,137
@material-ui/core/TrapFocus	0.00%	0.00%	3,834	3,834	1,613	1,613
@material-ui/core/styles/createMuiTheme	0.00%	+0.02% 🔺	16,386	16,386	5,827	5,828
@material-ui/core/useMediaQuery	0.00%	0.00%	2,541	2,541	1,058	1,058
@material-ui/lab	-0.00%	-0.01%	153,545	153,538	46,752	46,745
@material-ui/styles	0.00%	0.00%	51,492	51,492	15,304	15,304
@material-ui/system	+0.06% 🔺	-0.18%	15,658	15,668	4,366	4,358
Button	-0.00%	+0.02% 🔺	78,778	78,777	24,072	24,076
Modal	-0.01%	+0.18% 🔺	14,346	14,344	5,010	5,019
Portal	0.00%	0.00%	2,907	2,907	1,318	1,318
Rating	-0.00%	-0.01%	70,245	70,243	21,948	21,945
Slider	0.00%	-0.01%	74,483	74,483	23,064	23,062
colorManipulator	0.00%	0.00%	3,904	3,904	1,543	1,543
docs.landing	0.00%	0.00%	52,305	52,305	13,790	13,790
docs.main	0.00%	0.00%	597,545	597,545	190,886	190,886
packages/material-ui/build/umd/material-ui.production.min.js	-0.06%	-0.03%	300,602	300,416	86,485	86,462

Generated by 🚫 dangerJS against d2e24af

[oliviertassinari]

@ahtcx Great initiative! The dark mode colors were 🤢. I have tried to increase the visibility a bit. Let me know what you think of the changes!

[ahtcx]

@oliviertassinari I think that does help a bit, looks good to me 😀

[mbrookes]

@oliviertassinari Should the Slider match?

[oliviertassinari]

@mbrookes Ohhhh, yeah! Does it mean that we can use the opacity instead of a custom color 😍?

[oliviertassinari]

@mbrookes I'm out of options regarding how we can simplify the color approach. I have done my best. Any suggestion is welcome, otherwise, it should be good enough.

[oliviertassinari]

@ahtcx Thanks!