Rework of loki.source.file

[wildum]

The current implementation of the loki.source.file has some problems:

• It does not scale very well because, on every target update, we stop all the readers and re-create them (see the comment in the code https://github.com/grafana/alloy/blob/main/internal/component/loki/source/file/file.go#L165).
• it does not handle file rotations on Windows if the file has the same name (see Fix loki source file windows #2282)

I suggest reworking this component to use the runner pkg (like the loki.source.docker component) and adding a mechanism for the runners to periodically retry reading the file that they were assigned.

To improve it further, we could use a pool of workers to reduce the number of goroutines

[dehaansa]

Just linking issues: #2292