Use FluentBit Version as environment variable

**Is your feature request related to a problem? Please describe.**
I would like to use the FluentBit version (output of `fluent-bit -V`) as a environment variable inside the [record_modifier](https://docs.fluentbit.io/manual/pipeline/filters/record-modifier) just like $HOSTNAME or any other system environment variable.

**Describe the solution you'd like**
```
# fluent-bit -V
Fluent Bit v1.9.2
```
```
[FILTER]
Name record_modifier
Match *
Record hostname ${HOSTNAME}
Record fluentbit ${VERSION}
```

**Describe alternatives you've considered**
Changing the `fluent-bit.service` and setting the environment variable by hand. Unfortunately this kills the update possibility from the [APT repository](https://docs.fluentbit.io/manual/installation/linux).