[python] Keep REST catalog operations on Python

[JingsongLi]

Purpose

Keep PyPaimon's REST catalog operations on the Python HTTP client. These metadata calls do not benefit from a Native bridge, while Native table planning, reading, writing and committing continue to execute in Rust.

Changes

• Undo the Native REST branch delegation introduced by [python] Use Native REST catalog branch operations #10619 and remove the Native version-management bridge from earlier revisions of this PR.
• Call Python RESTApi directly for all branch, tag, snapshot-loading and rollback entry points.
• Delete the Native catalog adapter, its authentication/header reconstruction and the corresponding Rust SDK requirements in Native CI. This PR no longer depends on paimon-rust [license] LICENSE.animal-sniffer should not be standard MIT #1142.
• Retain the Java protocol corrections: omitted absent rollback guards, opaque pagination parameters, null versus empty tag pages, structured errors, and resource path validation.
• Replace Native-bridge-only tests with real Python HTTP tests. A guard forbids imports of pypaimon_rust during metadata calls, even when Native table options are enabled.
• Keep the shared Parquet/BLOB data-safety and uncertain-publication regressions using Native table reads/writes and Python catalog calls.
• Update the README to describe the execution boundary.

Rust's public REST catalog APIs remain in the independent paimon-rust PR.

Verification

• Python REST branch/version/tag/rollback suites: 174 passed, 3 Native-data tests skipped in the ordinary lane.
• Native table branch-write and Python REST regressions with Native planning, reading, writing and committing enabled: 146 passed.
• Added resource-path regressions: 6 passed, with no requests sent for parent-resource names.
• Flake8 and git diff --check passed.

[leaves12138]

LGTM