Remove global paths from logp file output

[`logp.makeFileOutput`](https://github.com/elastic/elastic-agent-libs/blob/3b9a0af/logp/core.go#L476-L503) resolves the log file path using `cfg.Paths.Resolve(paths.Logs, ...)`.

(some) Production callsites that configure file-based logging and are affected:

- [ ] **beats** — [`libbeat/cmd/instance/beat.go:799`](https://github.com/elastic/beats/blob/8f7210899f/libbeat/cmd/instance/beat.go#L799)
```go
configure.LoggingWithTypedOutputsLocal(b.Info.Beat, b.Config.Logging, b.Config.EventLogging, logp.TypeKey, logp.EventType)
```
- [ ] **apm-server** — [`internal/beatcmd/logging.go:68`](https://github.com/elastic/apm-server/blob/d044b9a92/internal/beatcmd/logging.go#L68)
```go
logp.Configure(logpConfig)
```
- [ ] **elastic-agent** — [`pkg/core/logger/logger.go:133`](https://github.com/elastic/elastic-agent/blob/8c43ad3338/pkg/core/logger/logger.go#L133)
```go
configure.LoggingWithTypedOutputs("", commonCfg, eventLoggercommonCfg, "log.type", "event", outputs...)
```
- [x] **elastic-agent** — [`internal/pkg/agent/cmd/watch.go:381`](https://github.com/elastic/elastic-agent/blob/5e3c865484/internal/pkg/agent/cmd/watch.go#L381)
```go
configure.LoggingWithOutputs("", libC, internal)
```

All reach `makeFileOutput` via the `createSink` → `createLogOutput` chain.

The most straightforward option is to add a path config option that callers need to use.