Allow retrieval of preceding row

Hi, I've been using a wrapper that includes the row immediately preceding a cycle or step as part of the dataset. It would be great to incorporate this functionality into PyProBE.

The following function can be used with filtering, for example:
- `filter_with_preceding_row(procedure, experiment=experiment_name)`
- `filter_with_preceding_row(experiment, cycle=i)`
- `filter_with_preceding_row(experiment, phase="discharge", step=i)`.

```
import polars as pl

def filter_with_preceding_row(
procedure,
experiment: str | None = None,
cycle: int | None = None,
phase: str | None = None,
step: int | None = None,
):
"""
Obtain the PyProBE result including the preceding row of the data.
"""
data = procedure
if experiment is not None:
data = data.experiment(experiment)
if cycle is not None:
data = data.cycle(cycle)
if phase is not None:
if phase == "discharge":
data = data.discharge()
elif phase == "charge":
data = data.charge()
elif phase == "rest":
data = data.rest()
else:
raise ValueError("Unrecognised phase")
if step is not None:
data = data.step(step)

# Add the preceding row
start_time = data.lf.select("Time [s]").first().collect().item()
preceding_row = procedure.lf.filter(pl.col("Time [s]") < start_time).last()
data.lf = pl.concat((preceding_row, data.lf), how="diagonal_relaxed")

return data
```

Start by reviewing the proposed filter_with_preceding_row wrapper and the existing experiment, cycle, phase, and step filtering entry points. Compare this request with linked pull request #382; done means filtered results include the immediately preceding row without changing the requested filtering behavior.

Written by the indexing model from the issue text.