Move `StringPool` to `wasmtime-environ` #36023

Job	Run time
Rustfmt	31s
Check JS	10s
Clippy	6m 35s
Determine CI jobs to run	14s
Clang format	11s
Monolith Checks	3m 10s
Check wasmtime-bench-api	1m 33s
Check cranelift-entity	34s
Check wasmtime-cli	6m 5s
Check wasmtime-wasi	1m 54s
Check cranelift-codegen	1m 18s
Check wasmtime-c-api	1m 25s
Check wasmtime	6m 11s
Check wasmtime-wasi-http	3m 49s
Check wasmtime-wizer	2m 7s
Check wasmtime-fiber	33s
Test Linux x86_64 (wasmtime)	2m 27s
Test Linux x86_64 (3/6)	7m 12s
Test Linux x86_64 (wasmtime-wasi)	6m 31s
Test Linux x86_64 (wasmtime-cli)	13m 10s
Cargo deny	0s
Test Linux x86_64 (1/6)	9m 47s
Test Linux x86_64 (2/6)	4m 40s
Test wasi-tls using native-tls & openssl providers	0s
Test wasi-nn (${{ matrix.feature }}, ${{ matrix.os }})	0s
Miri	0s
Platform: ${{ matrix.target }}	0s
Meta deterministic check	-1s
Cargo vet	-1s
Nightly tests	-1s
Doc build	-1s
Test the min-platform example	-1s
Test wasmtime-fuzzing	-1s
verify-publish	-1s
Build wasi-preview1-component-adapter	-1s
Release build for ${{ matrix.build }}	-1s
One-off special tests	-1s
Test C-API ${{ matrix.name }}	-1s
Build wasi-preview1-component-adapter-provider	-1s
Cargo vet failed on a Pull Request	-1s
Run benchmarks	-1s
Test DWARF debugging	-1s
Record the result of testing and building steps	3s
File an issue if this build failed and was cron-triggered	-1s
push-tag	-1s
	1h 19m 53s

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