Remove uuid dependency

[larseggert]

uuid pulls in a bunch of WASM dependencies, even when Codspeed is pulled in with default-features = false. For some projects, that means vetting a lot of extra code.

This PR replaces the uuid dependency and uses getrandom to generate an UUIDv4-style string. (I'm not sure if anything depends on things being named with UUIDs; if not, this PR would be even simpler.)

[codspeed-hq]

CodSpeed Performance Report

Merging #148 will degrade performances by 52.5%

_{Comparing larseggert:remove-uuid-dependency (d491963) with main (6c92e06)}

Summary

⚡ 4 improvements
❌ 1 (👁 1) regression
✅ 367 untouched

Benchmarks breakdown

	Mode	Benchmark	BASE	HEAD	Change
⚡	WallTime	fibonacci_custom_measurement	421 ns	407 ns	+3.44%
⚡	Simulation	count_chars_in_string	730.3 ns	701.1 ns	+4.16%
⚡	WallTime	permutations[7]	828.7 µs	788.3 µs	+5.13%
⚡	WallTime	sleep_100ns	61.8 µs	16.5 µs	×3.8
👁	WallTime	sleep_1us	29.9 µs	62.9 µs	-52.5%

[GuillaumeLagrange]

@larseggert good catch, thanks for the PR !