fix: issues parsing with 'preserveLatex' set to 'true'

[samueltlg]

Noticed that verbatimLatex not being saved on BoxedExpression instances created from ce.parse for some time. Looks as if this traceable to commits:

cd557e5 - 'arch: changed JSON canonical format, APIs for serialization to LaTeX and MathJSON' (2024-06-25)

^Wherein there is retraction of passing of 'metadata' to ce.box from within ce.parse
And:

e1f9e19 - 'arch' (2024-09-25)

^In which 'metadata' is retracted both as an argument to 'box' (the function) and its inner forwarding to BoxedExpression constructor calls when handling 'MathJSON object literals'.

As a guess, it appears to me that removing metadata as a parameter from box was apt due to these properties being foreseen as present on MathJSON object literals: if present at all. Looks however that in these changes that the step of checking for this meta elsewhere (i.e. object literals) and forwarding onwards (like before) is absent.
This 'fix' is only an educated guess & seems to address the issue,

But this change/request also appears to break a single test-case within test/compute-engine/latex-syntax/numbers.test.ts - which I have not investigated - and thus is not suitable for merging.
(Note at the time of this request, the HEAD of main (#115272d, there is already extant a single test failure (test/compute-engine/functions.test.ts -> Apply -> Function and Hold), which is not related to this change).

Single commit also includes an unused utility isExpressionObject, which was initially used, but could now be discarded.

(Could also do with a couple of test cases for this feature)

[arnog]

On first reading, this looks like a good PR. Curious to see which test case breaks because of it.

[arnog]

The PR is still a draft, and therefore cannot be merged. Let me know when it's ready for review.

[samueltlg]

The PR is still a draft, and therefore cannot be merged. Let me know when it's ready for review.

Apologies; I did think it was already ready to be merged.

I just did some investigation into why the breaking test-case, & I think it appears that everything is otherwise fine.
The reason for this particular matcher failure is because parsing of '1.0' with function parseVal within 'compute-engine/latex-syntax/numbers.test.ts', when parsing this with meta-data (now the default), results in this being a number (ExactNumericValue, to be precise), rather than a 'ce.one' instance. Consequently, through parseVal, the string-form of its numericValue is returned being "1", rather than the expected number-literal 1; so maybe just a little tweak somewhere.

Just marking it as ready, anyway