perf(blooms): Avoid tiny string allocations for insert cache

[chaudum]

What this PR does / why we need it:

Given that we see really high insert cache hit rate, we can void the string allocations for the cache ownership check.

sum(rate(loki_bloom_inserts_total{collision="cache"}[$__rate_interval]))
/
sum(rate(loki_bloom_inserts_total{}[$__rate_interval]))

Special notes for your reviewer:

Running benchmark with command:

$ gotest -v -count=10 ./pkg/storage/bloom/v1/... -test.run=^$ -test.bench=BenchmarkPopulateSeriesWithBloom

Results:

$ benchstat bench-old.txt bench-new.txt 
bench-old.txt:5: missing iteration count
bench-new.txt:5: missing iteration count
goos: linux
goarch: amd64
pkg: github.com/grafana/loki/v3/pkg/storage/bloom/v1
cpu: 11th Gen Intel(R) Core(TM) i7-1185G7 @ 3.00GHz
                          │ bench-old.txt │           bench-new.txt            │
                          │    sec/op     │   sec/op     vs base               │
PopulateSeriesWithBloom-8   1038.9µ ± 29%   973.7µ ± 2%  -6.28% (p=0.000 n=10)

                          │ bench-old.txt │            bench-new.txt            │
                          │     B/op      │     B/op      vs base               │
PopulateSeriesWithBloom-8    9.112Mi ± 0%   9.054Mi ± 0%  -0.64% (p=0.000 n=10)

                          │ bench-old.txt │           bench-new.txt            │
                          │   allocs/op   │ allocs/op   vs base                │
PopulateSeriesWithBloom-8     5269.0 ± 0%   877.0 ± 0%  -83.36% (p=0.000 n=10)

Checklist

• Reviewed the CONTRIBUTING.md guide (required)
• Documentation added
• Tests updated
• Title matches the required conventional commits format, see here
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[chaudum]

@owen-d Can you take a look as well? Feel free to merge it thereafter.

[owen-d]

note: The []byte is reused across Next calls. I wonder if this impacts us here.

// The Token iterator uses shared buffers for performance. The []byte returned by At()
// is not safe for use after subsequent calls to Next()

[chaudum]

The unsafe string is only used for the membership check, not the assignment in the map.

[owen-d]

Oh good point. LGTM

[owen-d]

Oh good point. LGTM