Use pygraphviz to render pass manager drawings (step 1 of #16544)

[VedantMahadik-qc]

AI/LLM disclosure

• I didn't use LLM tooling or only used it privately.
• I used the following tool to help write this PR description:
• I used the following tool to generate or modify code:

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Implements step 1 of the plan @1ucian0 outlined in #16544: adds 'pygraphviz' as a new optional dependency and removes the requirement for a manually installed system Graphviz when drawing pass managers.

Changes

• New 'HAS_PYGRAPHVIZ' lazy tester in 'qiskit.utils.optionals' (with docs entry).
• 'pass_manager_drawer' / 'staged_pass_manager_drawer' now require pygraphviz instead of system Graphviz. Graph construction still uses pydot (removing pydot is step 2, pending the rustworkx question); rendering now hands the DOT source to pygraphviz, whose 2.0+ wheels bundle the Graphviz binaries.
• Added 'pygraphviz>=2.0' to the 'visualization' extra and 'optionals-interactive' group (2.0 is the first release with bundled binaries).
• Updated test skip conditions and added a release note.

Windows wheel confirmation

On Windows 11 / Python 3.11 with no system Graphviz installed, 'pip install pygraphviz' fetched the prebuilt 'pygraphviz-2.0.1-cp311-win_amd64' wheel, and 'pass_manager_drawer' rendered successfully end-to-end – which is the platform confirmation step 1 is meant to provide.

Also fixes a latent Windows bug

Testing this path exposed a pre-existing issue: 'make_output' called 'os.remove' on the temporary PNG while 'PIL.Image.open's' lazy file handle was still open, raising 'PermissionError' on Windows. The image is now loaded via a context manager and copied in-memory. (This predates this PR but was unreachable in practice, since the drawer previously required a system Graphviz install that Windows users rarely had.)

'test_pass_manager_drawer.py' passes 2/2 locally on Windows — these tests were previously always skipped on this platform.

The rustworkx-based call sites ('dag_visualization.py', 'gate_map.py', etc.) still legitimately require 'HAS_GRAPHVIZ', so that tester is unchanged. If this goes beyond step 1, I'm happy to trim it back.

Part of #16544 (step 2 - moving off pydot/dot-calls to follow separately).

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