## Take one bulk string with spaces for MULTI_ARG configs parsing
Currently redis-server looks for arguments that start with `--`,
and anything in between them is considered arguments for the config.
like: `src/redis-server --shutdown-on-sigint nosave force now --port 6380`
MULTI_ARG configs behave differently for CONFIG command, vs the command
line argument for redis-server.
i.e. CONFIG command takes one bulk string with spaces in it, while the
command line takes an argv array with multiple values.
In this PR, in config.c, if `argc > 1` we can take them as is,
and if the config is a `MULTI_ARG` and `argc == 1`, we will split it by spaces.
So both of these will be the same:
```
redis-server --shutdown-on-sigint nosave force now --shutdown-on-sigterm nosave force
redis-server --shutdown-on-sigint nosave "force now" --shutdown-on-sigterm nosave force
redis-server --shutdown-on-sigint nosave "force now" --shutdown-on-sigterm "nosave force"
```
## Allow options value to use the `--` prefix
Currently it decides to switch to the next config, as soon as it sees `--`,
even if there was not a single value provided yet to the last config,
this makes it impossible to define a config value that has `--` prefix in it.
For instance, if we want to set the logfile to `--my--log--file`,
like `redis-server --logfile --my--log--file --loglevel verbose`,
current code will handle that incorrectly.
In this PR, now we allow a config value that has `--` prefix in it.
**But note that** something like `redis-server --some-config --config-value1 --config-value2 --loglevel debug`
would not work, because if you want to pass a value to a config starting with `--`, it can only be a single value.
like: `redis-server --some-config "--config-value1 --config-value2" --loglevel debug`
An example (using `--` prefix config value):
```
redis-server --logfile --my--log--file --loglevel verbose
redis-cli config get logfile loglevel
1) "loglevel"
2) "verbose"
3) "logfile"
4) "--my--log--file"
```
### Potentially breaking change
`redis-server --save --loglevel verbose` used to work the same as `redis-server --save "" --loglevel verbose`
now, it'll error!
bfbb15f75d