fix: Use depth in stacktrace length calc

[paulz]

Goal

Fixes #357

Design

Use top level dictionary to store depth

Changeset

Extracted report tests into a separate file

Tests

Unit test

Updated test expectations as per @kattrali comment:
#359 (comment)

Review

Outstanding Questions

• Added a changelog entry? Not yet

• This pull request is ready for:
  • Initial review of the intended approach, not yet feature complete
  • Structural review of the classes, functions, and properties modified
  • Final review

• The correct target branch has been selected (master for fixes, next for
  features)
• Consistency across platforms for structures or concepts added or modified
• Consistency between the changeset and the goal stated above
• Internal consistency with the rest of the library - is there any overlap between existing interfaces and any which have been added?
• Usage friction - is the proposed change in usage cumbersome or complicated?
• Performance and complexity - are there any cases of unexpected O(n^3) when iterating, recursing, flat mapping, etc?
• Concurrency concerns - if components are accessed asynchronously, what issues will arise
• Thoroughness of added tests and any missing edge cases
• Idiomatic use of the language

[kattrali]

Per some in-person discussion, PR is ready pending:

• Rebase against latest changes
• Adding a functional test for changing depth via notify with block

[kattrali]

Added a small change in 0f73076 to test against the demangled Swift method name rather than the mangled one for both ease of readability and to reduce breakage later. Testing the mangled name failed for me locally because it was different by a single letter.

Looks good, next time let's get the changeset smaller by splitting up the tangentially related changes into separate PRs (renaming files, etc)