Support scanning a specific branch of a table

### Feature Request / Improvement

As far as I can tell, PyIceberg does not directly support being able to scan a particular branch of an iceberg table. For example, there is no way to be able to run an equivalent of queries like

SELECT * FROM `..;`

as documented in https://iceberg.apache.org/docs/1.8.0/branching/#schema-selection-with-branches-and-tags

I can see that PR #941 to add support to _write_ to branches in Pyiceberg is well on its way to be being merged in, so this would be a useful complement.

Alternatively, perhaps I'm mistaken and there is already a way to do this, but it wasn't clear in the documentation

Start by reading the Iceberg branching and schema-selection documentation linked in the issue, then review PR #941 for the existing branch-writing support. Inspect the current PyIceberg scan API and determine how a branch-qualified table should be selected; done means callers can scan a specific table branch as in the documented query example.

Written by the indexing model from the issue text.