feat: add current_title and reference_title to RenderOptions

[SuryaSunil1326]

Summary

Closes #820.

Adds current_title (default Current) and reference_title (default Reference) fields to RenderOptions, making the dataset labels in all data-drift visualizations configurable instead of hardcoded.

Changes:

• RenderOptions in legacy/options/agg_data.py — two new fields with backwards-compatible defaults
• plot_scatter_for_data_drift in legacy/utils/visualizations.py — accepts current_title parameter
• ColumnDriftMetric, DataDriftTable, TextDescriptorsDriftMetric renderers — pass current_title through to scatter plots
• ColumnValuePlot renderer — passes both titles to the raw scatter render method
• TargetByFeaturesTable renderer — passes both titles to regression/classification figure helpers

Usage

from evidently.legacy.options.agg_data import RenderOptions
from evidently.legacy.options.base import Options
from evidently.legacy.report import Report
from evidently.legacy.metrics import ColumnDriftMetric

report = Report(
    metrics=[ColumnDriftMetric(column_name=col)],
    options=Options(render=RenderOptions(current_title=Production, reference_title=Training)),
)

Test plan

• Added test_column_drift_metric_custom_titles — runs a ColumnDriftMetric report with custom titles and verifies the dashboard builds without error
• All existing tests in tests/metrics/data_drift/test_column_drift_metric.py still pass