remove consts from tsk_json_struct_metadata_get_blob (closes #3425)

[petrelharp]

As discussed in #3425, it is maybe helpful to remove the const from some of the arguments to tsk_json_struct_metadata_get_blob.

My superficial understanding of the issue is as follows: suppose you have a function that accepts a pointer, say *blob, and doesn't modify the stuff that pointer points at. Then it's fine to define your function to accept const foo *blob but then pass it in a non-const foo *blob from somewhere else, since const is supposed to mean "we don't change this here" not "we don't change this anywhere". However if it takes a pointer-to-a-pointer, say const foo **blob then there are ways that you'd actually be able to modify the contents being ultimately pointed at without, like, noticing. So it is not cool to pass in foo **blob.

So, I agree - seems like we should indeed remove the const.

According to this page the "most common solution" is to declare it like const foo* const *blob; however, I think this means you can't change the pointer *blob either and we do indeed need to do that in this function. And I tried it and it doesn't seem to work.

So here I've removed the const from **blob. This meant I also needed to remove const from **json and *metadata, since these are all pointing at the same chunk of memory.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.92%. Comparing base (1835ea3) to head (c531bfa).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3427   +/-   ##
=======================================
  Coverage   91.92%   91.92%           
=======================================
  Files          37       37           
  Lines       32153    32153           
  Branches     5143     5143           
=======================================
  Hits        29556    29556           
  Misses       2264     2264           
  Partials      333      333           

Flag	Coverage Δ
C	82.70% <100.00%> (ø)
c-python	77.34% <0.00%> (ø)
python-tests	96.40% <ø> (ø)
python-tests-no-jit	33.22% <ø> (ø)

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Components	Coverage Δ
Python API	98.69% <ø> (ø)
Python C interface	91.23% <ø> (ø)
C library	88.86% <100.00%> (ø)

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[bhaller]

I'm not sure what this means: "github-merge-queue bot removed this pull request from the merge queue due to no response for status checks". But it looks like it passed all checks, and the PR looks good to me. Can this merge be bumped somehow?

[petrelharp]

I suspect maaaaybe github's automated stuff dropped the ball? Trying again; will manually merge if not.

[bhaller]

I suspect maaaaybe github's automated stuff dropped the ball? Trying again; will manually merge if not.

The auto-merge seems to have failed again. Maybe there's a time limit for all the checks to complete, and if they don't finish within that time limit the auto-merge gets cancelled? In which case that time limit needs to get extended somehow/somewhere, otherwise the auto-merge is seeming pretty useless. :-> Anyhow, manual merge for now, I guess?