Reset `analysis.workflows.functionWorkflow` to `core.function.metaAnalysis` if set to `core.function.objectiveC`

Version and Platform (required):

• Binary Ninja Version: 5.3.8713-dev Ultimate, a40c2e7b
• OS: macos
• OS Version: 26.1.0
• CPU Architecture: arm64

Bug Description:
If a user explicitly set analysis.workflows.functionWorkflow to core.function.objectiveC in Binary Ninja 5.1 or earlier, they'll get some surprising / broken behavior when opening binaries in 5.2 or newer. core.function.objectiveC no longer exists, and instead the Objective-C activities are registered on the meta workflow.

Steps To Reproduce:
Untested, but presumably:

1. Set analysis.workflows.functionWorkflow to core.function.objectiveC (or some other workflow that does not exist).
2. Open a binary.

Expected Behavior:
Something sensible.

For core.function.objectiveC we should reset the setting to the default value of core.function.metaAnalysis. The Objective-C workflow was removed in 5.2.

For other values that do not correspond to a workflow that is registered we may want to leave the setting value as-is, log a warning or error, but then use core.function.metaAnalysis anyway. This would handle the case where a named workflow is registered by a plug-in that is no longer available, perhaps due to needing to rebuild due to an ABI bump or due to launching with user plug-ins disabled.

Actual Behavior:
Many thousands of errors, and no functions in linear view.

Additional Information:
Originally reported by a user on Slack.

Start by locating the handling of analysis.workflows.functionWorkflow and the registry of registered workflows. Reproduce the legacy core.function.objectiveC setting if possible, then verify that it falls back to core.function.metaAnalysis without generating errors or leaving functions unavailable; also determine the intended behavior for other unregistered workflow names.