Fix symtab json file removal and reduce regression scope

[celinval]

Description of changes:

This fixes a regression introduced in #2439 when write symtab json is enabled. We still need to take that into consideration and remove them if needed.

This change also simplifies the write symtab json regression to avoid the out of disk space issue we've been seeing since #2439.

Resolved issues:

N/A

Related RFC:

N/A.

Call-outs:

IMHO, we should consider removing support for the symtab json option given how much slower and costly it is. Besides, we haven't had any major problem with the goto approach that justifies keeping this code lingering.

Until then, we still want to have some test coverage in our regression, but keeping a full regression is costly and just not worth it at this point. Another possible way to fix the out of disk issue would be to clean the build folder after each test suite, but this would be a much more invasive change to our scripts.

Testing:

• How is this change tested? CI

• Is this a refactor change?

Checklist

• Each commit message has a non-empty body, explaining why the change was made
• Methods or procedures are documented
• Regression or unit tests are included, or existing tests cover the modified code
• My PR is restricted to a single feature or bugfix

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