refactor(js_grammar): improve representation of imports

[Conaclos]

Summary

This implements the proposal I made in the corresponding discussion.

This refactoring provides several advantages:

• the CST is now closer to the spec
• the following invalid states cannot be represented (which is more in line with the philosophy of Biome)

  import type A, { B } from "";
  import type A, * as B from "";

• there is a single way to represent a namespace import

Test Plan

I updated the parser tests and the associated snapshots.

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[github-actions]

Parser conformance results on

js/262

Test result	main count	This PR count	Difference
Total	49701	49701	0
Passed	48721	48721	0
Failed	980	980	0
Panics	0	0	0
Coverage	98.03%	98.03%	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	6322	6322	0
Passed	2036	2036	0
Failed	4286	4286	0
Panics	0	0	0
Coverage	32.20%	32.20%	0.00%

ts/babel

Test result	main count	This PR count	Difference
Total	662	662	0
Passed	592	592	0
Failed	70	70	0
Panics	0	0	0
Coverage	89.43%	89.43%	0.00%

ts/microsoft

Test result	main count	This PR count	Difference
Total	17646	17646	0
Passed	13452	13452	0
Failed	4192	4192	0
Panics	2	2	0
Coverage	76.23%	76.23%	0.00%

[Conaclos]

This is no longer reported because this is recovered as a combined import clause (defer is the default specifier). Not sure why it didn't error asking for a comma?

[Conaclos]

This change is responsible for the behavior change discussed here

[denbezrukov]

🦄