Docs: Update information about metrics mode

[psvri]

I noticed that there is currently no documentation describing the various metrics modes that can be configured for a table via the table properties write.metadata.metrics.default and write.metadata.metrics.column.col1. With the introduction of file format api , it would be helpful to document this to provide clearer guidance for integrators using this API.

[pvary]

Suggested change

	Notes:
	1. Metrics modes are explained below:
	- `none`: In this mode, `value_counts`, `null_value_counts`, `nan_value_counts`, `lower_bounds`, and `upper_bounds` are not persisted.
	- `counts`: In this mode, `value_counts`, `null_value_counts`, and `nan_value_counts` are persisted.
	- `truncate(length)`: In this mode, `value_counts`, `null_value_counts`, `nan_value_counts`, truncated `lower_bounds`, and truncated `upper_bounds` are persisted. Only string and binary values are truncated to the specified length. For other types, values are written as is.
	- `full`: In this mode, `value_counts`, `null_value_counts`, `nan_value_counts`, full `lower_bounds`, and full `upper_bounds` are persisted.
	Notes:
	1. Available metrics modes:
	- none: No metrics are persisted
	- counts: Only count metrics are persisted (value_counts, null_value_counts, nan_value_counts).
	- truncate(length): Persists counts plus truncated bounds (lower_bounds, upper_bounds). Truncation applies only to string and binary types; all other types are stored as-is.
	- full: Persists all metrics, including full lower_bounds and upper_bounds.