[Feature] Discussion the priority of Paimon Dynamic Options and Table Identifier

### Search before asking

- [x] I searched in the [issues](https://github.com/apache/paimon/issues) and found nothing similar.

### Motivation

Consider the following usage：

set spark.paimon.branch=A;
select * from `default`.`T$branch_B`;

When loading a table, the branch selection logic is: extraOtions > dynamicConf > Identifier

### Solution

_No response_

### Anything else?

_No response_

### Are you willing to submit a PR?

- [ ] I'm willing to submit a PR!

The issue describes branch selection while loading a table, using Spark configuration and table identifiers, but names no files, tests, or entry points. First clarify the intended priority among extraOptions, dynamicConf, and Identifier, then identify the table-loading code and tests that cover these inputs. Done means the precedence is agreed and reflected in tested behavior.

Written by the indexing model from the issue text.