Change IPeak python export to be shared_ptr instead of raw pointer

[rosswhitfield]

Description of work

Fix segfault when accessing Peak from python after PeaksWorkspace has been deleted. This bug has existed in Mantid since at least Mantid 3.10.

By changing IPeak to be a shared_ptr the peaks workspace will exist as long a the python Peak's continue to exist. So this will fixes the segfault.

Closes #31345

To test:

This causes a segfault that should now be fixed

import time
from mantid.simpleapi import CreatePeaksWorkspace, DeleteWorkspace
peaks=CreatePeaksWorkspace(OutputType="LeanElasticPeak")
p=peaks.getPeak(0)
print(p.getScattering())
DeleteWorkspace(peaks)
time.sleep(1)
print(p.getScattering())

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[Copilot]

Pull request overview

This PR updates the Mantid Python bindings for IPeaksWorkspace.getPeak() (and peak iteration) so that Python IPeak objects hold shared ownership of the originating workspace, preventing use-after-free crashes when the workspace is deleted from the ADS. This addresses the long-standing Python segmentation fault described in #31345.

Changes:

• Changed the IPeaksWorkspace.getPeak() Python export to return an aliasing std::shared_ptr<IPeak> that co-owns the workspace.
• Updated the Python iterator for peaks workspaces to return the same shared-ownership peak handles.
• Added Python unit tests to verify peak usability after DeleteWorkspace and that peak modifications remain reflected in the workspace.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
Framework/PythonInterface/mantid/api/src/Exports/IPeaksWorkspace.cpp	Updates Boost.Python bindings to return peaks as aliasing shared_ptr handles and adjusts iteration to preserve workspace lifetime.
Framework/PythonInterface/mantid/api/src/Exports/IPeak.cpp	Registers std::shared_ptr<IPeak> for Boost.Python conversions to support the new return type.
Framework/PythonInterface/test/python/mantid/api/IPeaksWorkspaceTest.py	Adds regression tests covering post-deletion peak access and ensuring workspace-reflective peak mutation semantics.