fix(project): change how extends should be applied

[ematipico]

Summary

Closes #343

When I implemented the feature, I implemented it with an incorrect assumption, where extends would override the current configuration.

Instead, extends should be computed first, and then on top of the result, we should apply the options of biome.json file.

To achieve this, I had to create a new method called merge_if_not_default. This was needed to avoid default values overriding what was computed from the extends.

Test Plan

I added a new test case, similar to the one of the issue that is closed. The snapshot shows that Biome format the code that correct options.

[github-actions]

Parser conformance results on

js/262

Test result	main count	This PR count	Difference
Total	48863	48863	0
Passed	47808	47808	0
Failed	1055	1055	0
Panics	0	0	0
Coverage	97.84%	97.84%	0.00%

jsx/babel

Test result	main count	This PR count	Difference
Total	40	40	0
Passed	37	37	0
Failed	3	3	0
Panics	0	0	0
Coverage	92.50%	92.50%	0.00%

symbols/microsoft

Test result	main count	This PR count	Difference
Total	6212	6212	0
Passed	2030	2030	0
Failed	4182	4182	0
Panics	0	0	0
Coverage	32.68%	32.68%	0.00%

ts/babel

Test result	main count	This PR count	Difference
Total	639	639	0
Passed	571	571	0
Failed	68	68	0
Panics	0	0	0
Coverage	89.36%	89.36%	0.00%

ts/microsoft

Test result	main count	This PR count	Difference
Total	17224	17224	0
Passed	13123	13123	0
Failed	4101	4101	0
Panics	0	0	0
Coverage	76.19%	76.19%	0.00%