[TreeItem] Use the ‘endIcon’ prop where appropriate

[chocolatl]

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

Closes #17476

[mui-pr-bot]

Details of bundle changes.

Comparing: e91f970...d60a7ae

bundle	parsed diff	gzip diff	prev parsed	current parsed	prev gzip	current gzip
@material-ui/core	0.00%	0.00%	331,962	331,962	90,633	90,633
@material-ui/core/Paper	0.00%	0.00%	68,660	68,660	20,458	20,458
@material-ui/core/Paper.esm	0.00%	0.00%	62,098	62,098	19,203	19,203
@material-ui/core/Popper	0.00%	0.00%	28,397	28,397	10,159	10,159
@material-ui/core/Textarea	0.00%	0.00%	5,082	5,082	2,132	2,132
@material-ui/core/TrapFocus	0.00%	0.00%	3,766	3,766	1,596	1,596
@material-ui/core/styles/createMuiTheme	0.00%	0.00%	16,348	16,348	5,818	5,818
@material-ui/core/useMediaQuery	0.00%	0.00%	2,488	2,488	1,050	1,050
@material-ui/lab	0.00%	-0.00%	154,783	154,783	46,921	46,920
@material-ui/styles	0.00%	0.00%	51,420	51,420	15,288	15,288
@material-ui/system	0.00%	0.00%	15,581	15,581	4,351	4,351
Button	0.00%	0.00%	78,633	78,633	24,021	24,021
Modal	0.00%	0.00%	14,542	14,542	5,114	5,114
Portal	0.00%	0.00%	2,907	2,907	1,318	1,318
Rating	0.00%	0.00%	69,963	69,963	21,856	21,856
Slider	0.00%	0.00%	75,084	75,084	23,184	23,184
colorManipulator	0.00%	0.00%	3,835	3,835	1,519	1,519
docs.landing	0.00%	0.00%	54,267	54,267	14,345	14,345
docs.main	0.00%	0.00%	597,961	597,961	191,048	191,048
packages/material-ui/build/umd/material-ui.production.min.js	0.00%	0.00%	302,849	302,849	87,078	87,078

Generated by 🚫 dangerJS against d60a7ae

[mbrookes]

Does this warrant a test?

[oliviertassinari]

Does this warrant a test?

This is probably @joshwooding to say :).

[eps1lon]

Does this warrant a test?

After something already broke? I hope so.

[joshwooding]

We should probably add tests that the icon override props work.

[oliviertassinari]

I have added a test case; we should be able to improve it in the future.

[oliviertassinari]

@chocolatl Thanks