Encoding circuits

[pehamTom]

Description

This PR introduces major changes to encoding circuit (and by extension state preparation circuit) synthesis. Main features are:

• Unification of Encoding- and Stateprep circuit synthesis
• Synthesis of non-CSS Clifford encoding isometries
• Improved rollout heuristics for improved gate-count and depth in synthesized Clifford circuits
• Extendable synthesis framework

Checklist:

• The pull request only contains commits that are focused and relevant to this change.
• I have added appropriate tests that cover the new/changed functionality.
• I have updated the documentation to reflect these changes.
• I have added entries to the changelog for any noteworthy additions, changes, fixes, or removals.
• I have added migration instructions to the upgrade guide (if needed).
• The changes follow the project's style guidelines and introduce no new warnings.
• The changes are fully tested and pass the CI checks.
• I have reviewed my own code changes.

[codecov]

Codecov Report

❌ Patch coverage is 78.75145% with 548 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/mqt/qecc/circuit_synthesis/operations.py	64.1%	106 Missing ⚠️
src/mqt/qecc/circuit_synthesis/transvection.py	71.0%	71 Missing ⚠️
src/mqt/qecc/circuit_synthesis/synthesis_utils.py	20.5%	58 Missing ⚠️
src/mqt/qecc/codes/stabilizer_code.py	78.7%	52 Missing ⚠️
src/mqt/qecc/circuit_synthesis/elimination.py	79.3%	47 Missing ⚠️
src/mqt/qecc/codes/pauli.py	82.0%	45 Missing ⚠️
src/mqt/qecc/circuit_synthesis/cnot.py	73.4%	30 Missing ⚠️
src/mqt/qecc/circuit_synthesis/rollout.py	85.1%	28 Missing ⚠️
src/mqt/qecc/circuit_synthesis/encoding.py	94.4%	24 Missing ⚠️
src/mqt/qecc/codes/css_code.py	83.8%	23 Missing ⚠️
... and 7 more

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