Fix before_send/transport dotted-path resolution in Task SDK Sentry c…

[bujjibabukatta]

Fix [sentry] before_send/transport dotted-path config never resolved to a callable in Task SDK

Problem

ConfiguredSentry.prepare_to_enrich_errors() in
task-sdk/src/airflow/sdk/execution_time/sentry/configured.py resolves the
before_send/transport dotted-path config options into real callables only
inside an else branch guarded by if sentry_config_opts:.

conf.getsection("sentry") always returns a non-empty dict (schema defaults
such as sentry_on are always present), so that if is always true and the
else branch — the only place before_send/transport are ever resolved via
conf.getimport() — is unreachable dead code.

As a result, a configured before_send/transport dotted path is passed to
sentry_sdk.init() as a raw string instead of a callable. sentry_sdk then
raises TypeError: 'str' object is not callable internally when trying to
invoke it, which it swallows via capture_internal_exceptions() — so every
Sentry event is silently dropped with no error surfaced to the user.

This is a regression from Airflow 2.x's airflow/sentry.py, where the
equivalent conf.getimport(...) calls ran unconditionally. The branching
structure changed when this was ported to the Task SDK in #57032, making the
resolution path unreachable.

Fix

Make before_send/transport resolution unconditional, matching 2.x
behavior, while preserving the existing DSN handling and the
UNSUPPORTED_SENTRY_OPTIONS warning.

Testing

• Updated the three existing tests (test_prepare_to_enrich_errors,
  test_prepare_to_enrich_errors_with_executor_integration,
  test_custom_transport) that were asserting the unresolved dotted-path
  string was passed to sentry_sdk.init() — they now assert the resolved
  callable, which is effectively the regression test for this bug.
• No behavior change when before_send/transport aren't configured
  (test_minimum_config still passes unchanged).

closes: #69464