Automated Synthesis of Encoder Circuits for Stabilizer Codes

[pehamTom]

Description

This PR introduces functionality to automatically synthesize encoder circuits for arbitrary stabilizer codes. Since this is closely related to state preparation circuit synthesis, this PR refactors and unifies the respective synthesis methods into a circuit_synthesis module.

Planned Features:

• [x] Optimal (gate or depth) encoder circuit synthesis for CSS codes
• [x] Heuristic encoder circuit synthesis for CSS codes
• [ ] ~~Optimal (gate or depth) circuit synthesis for non-CSS ancilla states~~
• [ ] ~~Heuristic circuit synthesis for non-CSS ancilla states~~

The last parts were canceled because qecc functionality already allows for the construction of such state preparation circuits.

Checklist:

• [ ] The pull request only contains commits that are related to it.
• [ ] I have added appropriate tests and documentation.
• [ ] I have made sure that all CI jobs on GitHub pass.
• [ ] The pull request introduces no new warnings and follows the project's style guidelines.