Support non-deprecated `code.function.name` for code source

### Problem Statement

We are considering setting the non-deprecated `code.function.name` in the Python SDK.

Today the function displayed in the code source panel is only drawn from `code.function`.

Note that `code.function.name` is not equivalent to `code.function`, as `code.function.name` is the fully-qualified name [as per OTel](https://opentelemetry.io/docs/specs/semconv/registry/attributes/code/#code-function-name), while `code.function` is only the function identifier. That is, `code.function.name` includes both the values of the deprecated `code.namespace` and the deprecated `code.function`.

Setting `code.function`:

Setting `code.function.name`:

### Solution Brainstorm

_No response_

### Product Area

Explore

The issue does not identify a file, test, or entry point. Start by locating the code-source panel's handling of code.function in the Sentry Python SDK and compare it with the linked OpenTelemetry definition. Done means the panel supports the non-deprecated, fully qualified code.function.name value and its display behavior is covered by tests.

Written by the indexing model from the issue text.