There have been two bugs reported about the `else` and `elseif`
commands in the context of the tracing functionality and the json-v1
format (#23191#22315). In essence, the reported traces referred to
the layer of the stacktrace immediately on top of the expected ones.
This MR fixes both issues. My solution adds a new parameter to the
`PrintCommandTrace` function, `commandMissingFromStack`, that callers
can specify if the command they want to report a trace for is not a
regular part of the stack maintained in `cmMakefile`. This is only the
case for `else` and `elseif`. The other bug is fixed by having the
caller pass a `cmListFileBacktrace`, which helps in getting the right
lines, file names... for the reported command.
Fixes: #23191#22315
fd46db1745