Add safe shape checking to synth_cz_depth_line_mr

[jakelishman]

This was previously unverified, which could lead to Rust panicking if the matrix was taller than it was wide.

Fix #16152

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:

[qiskit-bot]

One or more of the following people are relevant to this code:

• @Qiskit/terra-core

[coveralls]

Coverage Report for CI Build 25499096380

Coverage decreased (-0.03%) to 87.602%

Details

• Coverage decreased (-0.03%) from the base build.
• Patch coverage: 7 of 7 lines across 1 file are fully covered (100%).
• 39 coverage regressions across 5 files.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

39 previously-covered lines in 5 files lost coverage.

File	Lines Losing Coverage	Coverage
crates/qasm2/src/parse.rs	24	96.21%
crates/qasm2/src/lex.rs	9	91.26%
crates/circuit/src/parameter/symbol_expr.rs	4	74.09%
crates/circuit/src/parameter/parameter_expression.rs	1	91.04%
crates/transpiler/src/passes/unitary_synthesis/decomposers.rs	1	94.71%

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Coverage Stats

Relevant Lines:	122069
Covered Lines:	106935
Line Coverage:	87.6%
Coverage Strength:	962102.32 hits per line

---

💛 - Coveralls

[ShellyGarion]

LGTM. thanks for fixing this so quickly!
@alexanderivrii - would you like to review it too?

[alexanderivrii]

LGTM!