fix(xpress): migrate remaining deprecated Xpress 9.8 API calls

[brunoficoxpress]

Changes proposed in this Pull Request

Several Xpress API calls used by the direct api path were still on the
lowercase API deprecated in Xpress 9.8, with no fallback to the new camelCase
names. Fixed those, and added a small test for the direct API.

Checklist

• AI-generated content is marked (see AGENTS.md).
• [n.a. ] Code changes are sufficiently documented; i.e. new functions contain docstrings and further explanations may be given in doc.
• Unit tests for new features were added (if applicable).
• [n.a. ] A note for the release notes doc/release_notes.rst of the upcoming release is included.
• I consent to the release of this PR's code under the MIT license.

[codspeed-hq]

Merging this PR will regress 2 benchmarks

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

⚡ 3 improved benchmarks
❌ 2 regressed benchmarks
✅ 170 untouched benchmarks
⏩ 175 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	Memory	test_to_lp[rolling-severity=0]	2.1 MB	2.9 MB	-28.17%
❌	Memory	test_to_lp[storage-n=250]	30.7 MB	36.3 MB	-15.54%
⚡	Memory	test_to_lp[merge_balance-severity=0]	3.2 MB	2.1 MB	+49.86%
⚡	Memory	test_to_lp[rolling-severity=50]	429.7 MB	319.5 MB	+34.51%
⚡	Memory	test_to_lp[masked-n=100]	2.7 MB	2 MB	+33.08%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing brunoficoxpress:fix/xpress-deprecated-api-calls (89ec178) with master (d610692)}

Footnotes

1. 175 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩