[o11y] Avoid cloning tail event when dispatching it to single tail worker

[fhanau]

This could be expensive for events that are large/require several memory allocations. This required fixing how we construct the jsrpc.method attribute, the approach there was never fully working which was shadowed by the event being cloned. Also drop an unused Attribute constructor.

[codspeed-hq]

CodSpeed Performance Report

Merging #5614 will improve performances by 12.86%

_{Comparing felix/112925-stw (2fc25b9) with main (235680b)}

Summary

⚡ 1 improvement
✅ 56 untouched
⏩ 30 skipped¹

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
⚡	Encode_ASCII_32[TextEncoder][0/0/32]	3.4 ms	3 ms	+12.86%

Footnotes

1. 30 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. ↩