perf(autoware_tensorrt_plugins): cache max sort workspace bounds

[mojomex]

Summary

Builds on the stream-ordered variant by caching the maximum sort-workspace bounds used by the TensorRT plugins.

This draft PR corresponds to the benchmarked variant ptv3-t18-no-thrust-no-alloc-no-sync-maxnumel-47bf5656f-20260506.
All PRs in this cohort target main; each later PR contains the changes benchmarked in the earlier ones.

Cohort

• perf(autoware_tensorrt_plugins): remove Thrust from sort kernels (ptv3-t18-no-thrust-c8f76ed-20260506)
• perf(autoware_tensorrt_plugins): keep SegmentCSR allocation-free (ptv3-t18-no-thrust-no-alloc-e9515b790-20260506)
• perf(autoware_tensorrt_plugins): keep plugin outputs stream-ordered (ptv3-t18-no-thrust-no-alloc-no-sync-13f3672a0-20260506)
• perf(autoware_tensorrt_plugins): cache max sort workspace bounds (ptv3-t18-no-thrust-no-alloc-no-sync-maxnumel-47bf5656f-20260506)
• fix(ptv3): set TensorRT max auxiliary streams to 1 (ptv3-t18-no-thrust-no-alloc-no-sync-maxnumel-maxauxstreams1)

Benchmarks

Source report: reports/2026-05-07_22-20-12/report.md

Total Latency Summary

Variant	Measurement	CPU mean (ms)	CPU p95 (ms)	CPU faster vs baseline	GPU mean (ms)	GPU p95 (ms)	GPU faster vs baseline	Mean voxels
ptv3-t18	series (7 x 50)	29.117	31.755	+0.0%	28.020	30.598	+0.0%	120572
ptv3-t18-no-thrust-c8f76ed-20260506	series (7 x 50)	27.559	28.502	+5.7%	26.416	27.306	+6.1%	120572
ptv3-t18-no-thrust-no-alloc-e9515b790-20260506	series (7 x 50)	26.874	28.863	+8.3%	25.741	27.665	+8.9%	120572
ptv3-t18-no-thrust-no-alloc-no-sync-13f3672a0-20260506	series (7 x 50)	26.278	27.471	+10.8%	25.140	26.288	+11.5%	120572
ptv3-t18-no-thrust-no-alloc-no-sync-maxnumel-47bf5656f-20260506	series (7 x 50)	26.214	26.642	+11.1%	25.084	25.488	+11.7%	120572
ptv3-t18-no-thrust-no-alloc-no-sync-maxnumel-maxauxstreams1	series (7 x 50)	25.378	25.984	+14.7%	24.230	24.792	+15.6%	120572
ptv3-t18-no-thrust-no-alloc-no-sync-maxnumel-maxauxstreams3	series (7 x 50)	26.809	28.083	+8.6%	25.614	26.849	+9.4%	120572

Relative Performance

[github-actions]

Thank you for contributing to the Autoware project!

🚧 If your pull request is in progress, switch it to draft mode.

Please ensure:

• You've checked our contribution guidelines.
• Your PR follows our pull request guidelines.
• All required CI checks pass before marking the PR ready for review.