Move syntax factory inside syntax editor

[Shourya742]

This PR moves SyntaxFactory inside SyntaxEditor and migrates all of its with_mapping usages to SyntaxEditor’s make variant. Some remnants of SyntaxFactory::without_mapping still remain; addressing them may require additional work, as most are tied to the broader migration to SyntaxEditor and can be handled later.

• The first commit introduces changes to SyntaxEditor, including the integration of SyntaxFactory.
• The second commit fixes constructor mapping issues encountered during the refactor.
• The third commit migrates assists. Although large, the changes are straightforward and intuitive.

part of #15710 and #18285

[ChayimFriedman2]

LGTM.

While I am generally against interior mutability, this time I support it to make SyntaxEditor not require a mutable reference to allow storing editor.make() in a variable, which is more pleasant to the eyes IMO. I'll leave it to you, though, if you want to do that or merge this as-is.

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[Shourya742]

LGTM.

While I am generally against interior mutability, this time I support it to make SyntaxEditor not require a mutable reference to allow storing editor.make() in a variable, which is more pleasant to the eyes IMO. I'll leave it to you, though, if you want to do that or merge this as-is.

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Adapted, introducing RefCell in SyntaxEditor, it’s now more pleasant to read, with an explicit variable for editor.make().

[ChayimFriedman2]

Thanks

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[ChayimFriedman2]

If nodes are going to carry a lifetime, this won't compile. It will need to accept an editor from the outside. Fine for this PR, though.