Directories in storage.path should take alias name of input when in use

**Is your feature request related to a problem? Please describe.**
When using alias names on an input, I would expect the directory structure in the storage.path to take on the alias, instead of the name.number of the input

**Describe the solution you'd like**
When an alias is specified, use it as the name for the directory structure

**Describe alternatives you've considered**
N/A

**Additional context**
I would expect the the following input to use /data/syslog_9080 instead of /data/syslog.0

```
@SET fbvar_parsers_file=/fluent-bit/etc/parsers.conf

[SERVICE]
parsers_file ${fbvar_parsers_file}
flush 1
storage.path /data/
storage.sync normal
storage.checksum off
storage.backlog.mem_limit 5M
storage.metrics on

[INPUT]
alias syslog_9080
tag syslog_9080
name syslog
mode udp
port 9080
parser syslog-rfc3164
source_address_key @metadata.source
storage.type filesystem
```

Start with the [INPUT] example and the storage.path setting, then trace how the input alias and name are selected when filesystem storage creates its directory. The change is complete when the shown configuration uses /data/syslog_9080 rather than /data/syslog, with behavior covered by a relevant regression test.

Written by the indexing model from the issue text.