fix(Box Component): Box clone not overriding child component styles

[zetsin]

Fix Box clone not overriding child component styles #15993 , by setting higher index(default 0) to insert Box style after.

ref https://cssinjs.org/jss-api/?v=v10.0.0-alpha.22#create-style-sheet

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

[oliviertassinari]

@zetsin Thanks for taking the time to look into the problem. The long term plan is to remove the clone prop thanks to #15561. If you have a style conflict, you probably don't want to use the Box for that specific case.

[mui-pr-bot]

Details of bundle changes.

Comparing: 783b693...504260c

bundle	parsed diff	gzip diff	prev parsed	current parsed	prev gzip	current gzip
@material-ui/core	0.00%	+0.01% 🔺	327,763	327,771	90,314	90,319
@material-ui/core/Paper	0.00%	0.00%	68,477	68,477	20,407	20,407
@material-ui/core/Paper.esm	0.00%	0.00%	61,761	61,761	19,190	19,190
@material-ui/core/Popper	0.00%	0.00%	28,942	28,942	10,407	10,407
@material-ui/core/Textarea	0.00%	0.00%	5,505	5,505	2,365	2,365
@material-ui/core/TrapFocus	0.00%	0.00%	3,753	3,753	1,576	1,576
@material-ui/core/styles/createMuiTheme	0.00%	0.00%	16,160	16,160	5,813	5,813
@material-ui/core/useMediaQuery	0.00%	0.00%	2,595	2,595	1,104	1,104
@material-ui/lab	0.00%	0.00%	138,027	138,027	42,562	42,562
@material-ui/styles	0.00%	0.00%	51,887	51,887	15,384	15,384
@material-ui/system	0.00%	0.00%	15,576	15,576	4,432	4,432
Button	0.00%	0.00%	81,161	81,161	24,779	24,779
Modal	0.00%	0.00%	14,551	14,551	5,102	5,102
Portal	0.00%	0.00%	3,471	3,471	1,573	1,573
Slider	0.00%	0.00%	75,100	75,100	23,309	23,309
colorManipulator	0.00%	0.00%	3,904	3,904	1,543	1,543
docs.landing	0.00%	0.00%	54,338	54,338	13,762	13,762
docs.main	0.00%	0.00%	647,863	647,863	204,220	204,220
packages/material-ui/build/umd/material-ui.production.min.js	0.00%	+0.01% 🔺	300,178	300,186	86,044	86,050

Generated by 🚫 dangerJS against 504260c

[oliviertassinari]

I'm closing. This change breaks the code of people providing a class name to the Box component. The specificity will be wrong. I would discourage abusing the clone prop instead.