Instead of storing the function names (in a badly named Vector<String>)
and source ranges separately, consolidate them into a new struct:
TracebackFrame. This makes it both easier to use now and easier to
extend in the future.
Unlike before we now keep each call frame's current node source range
in the traceback frame next to the function name, meaning we can display
line and column numbers outside of the VM and after the call stack is
emptied.
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
(...and ASSERT_NOT_REACHED => VERIFY_NOT_REACHED)
Since all of these checks are done in release builds as well,
let's rename them to VERIFY to prevent confusion, as everyone is
used to assertions being compiled out in release.
We can introduce a new ASSERT macro that is specifically for debug
checks, but I'm doing this wholesale conversion first since we've
accumulated thousands of these already, and it's not immediately
obvious which ones are suitable for ASSERT.
