fix(recording): address unterminated string in thread gathering logic

[tomlongridge]

Goal

Fixes #719 in gathering thread data for handled errors - the initial memory allocation was incorrectly proceeded by a strlen call with no initial terminator added.

Changeset

Changed the bsg_kscrw_i_resetThreadTraceData function from memseting all the data to just null-terminating at 0, which is sufficient for our needs.

Also re-worked the logic slightly to encapsulate all the memory management (including initial malloc) in bsg_kscrw_i_collectJsonData and also guarded against malloc failing.

Tests

Ran the example app with Malloc Scribble, Malloc Guard Edges and Guard Malloc enabled.

Also manually tested returning BSG_KSJSON_ERROR_CANNOT_ADD_DATA from bsg_kscrw_i_collectJsonData to ensure that the error was still delivered.