[Modal] Support theme default props

[ianschmitz]

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

Fixes #17333.

Adds back support that existed in v3 for supplying default props in the theme for the Modal component.

[mui-pr-bot]

Details of bundle changes.

Comparing: 93e9ab6...19a7c18

bundle	parsed diff	gzip diff	prev parsed	current parsed	prev gzip	current gzip
@material-ui/core	+0.02% 🔺	+0.02% 🔺	331,237	331,316	90,484	90,502
@material-ui/core/Paper	0.00%	+0.02% 🔺	68,774	68,774	20,485	20,490
@material-ui/core/Paper.esm	0.00%	-0.01%	62,148	62,148	19,214	19,212
@material-ui/core/Popper	0.00%	0.00%	28,466	28,466	10,188	10,188
@material-ui/core/Textarea	0.00%	0.00%	5,094	5,094	2,135	2,135
@material-ui/core/TrapFocus	0.00%	0.00%	3,834	3,834	1,617	1,617
@material-ui/core/styles/createMuiTheme	0.00%	0.00%	16,385	16,385	5,827	5,827
@material-ui/core/useMediaQuery	0.00%	-0.09%	2,558	2,558	1,067	1,066
@material-ui/lab	0.00%	-0.01%	153,209	153,209	46,684	46,681
@material-ui/styles	0.00%	+0.02% 🔺	51,494	51,494	15,304	15,307
@material-ui/system	0.00%	0.00%	15,668	15,668	4,361	4,361
Button	0.00%	0.00%	78,663	78,663	24,048	24,048
Modal	+1.86% 🔺	+2.35% 🔺	14,335	14,601	5,013	5,131
Portal	0.00%	0.00%	2,907	2,907	1,322	1,322
Rating	0.00%	-0.01%	70,016	70,016	21,864	21,862
Slider	0.00%	-0.01%	74,282	74,282	23,015	23,012
colorManipulator	0.00%	0.00%	3,904	3,904	1,543	1,543
docs.landing	0.00%	0.00%	52,253	52,253	13,780	13,780
docs.main	+0.01% 🔺	+0.03% 🔺	597,295	597,368	190,660	190,717
packages/material-ui/build/umd/material-ui.production.min.js	+0.02% 🔺	+0.04% 🔺	302,103	302,151	86,803	86,841

Generated by 🚫 dangerJS against 19a7c18

[eps1lon]

Thanks.

I feel like we want a useThemeProps hook anyway at some point.

[oliviertassinari]

I feel like we want a useThemeProps hook anyway at some point.

@eps1lon Yes, it's very likely that we will need to take this path.