refactor : --rm is ignored with stdout

`zstd` CLI has progressively moved to the policy of
ignoring `--rm` command when the output is `stdout`.
The primary drive is to feature a behavior more consistent with `gzip`,
when `--rm` is the default, but is also ignored when output is `stdout`.
Other policies are certainly possible, but would break from this `gzip` convention.

The new policy was inconsistenly enforced, depending on the exact list of commands.
For example, it was possible to circumvent it by using `-c --rm` in this order,
which would re-establish source removal.

- Update the CLI so that it necessarily catch these situations and ensure that `--rm` is always disabled when output is `stdout`.
- Added a warning message in this case (for verbosity 3 `-v`).
- Added an `assert()`, which controls that `--rm` is no longer active with `stdout`
- Added tests, which control the behavior, even when `--rm` is added after `-c`
- Removed some legacy code which where trying to apply a specific policy for the `stdout` + `--rm` case, which is no longer possible

programs/fileio.h

@@ -86,7 +86,7 @@ void FIO_setLdmMinMatch(FIO_prefs_t* const prefs, int ldmMinMatch);
 void FIO_setMemLimit(FIO_prefs_t* const prefs, unsigned memLimit);
 void FIO_setNbWorkers(FIO_prefs_t* const prefs, int nbWorkers);
 void FIO_setOverlapLog(FIO_prefs_t* const prefs, int overlapLog);
-void FIO_setRemoveSrcFile(FIO_prefs_t* const prefs, unsigned flag);
+void FIO_setRemoveSrcFile(FIO_prefs_t* const prefs, int flag);
 void FIO_setSparseWrite(FIO_prefs_t* const prefs, int sparse);  /**< 0: no sparse; 1: disable on stdout; 2: always enabled */
 void FIO_setRsyncable(FIO_prefs_t* const prefs, int rsyncable);
 void FIO_setStreamSrcSize(FIO_prefs_t* const prefs, size_t streamSrcSize);