Use HashMap instead of IndexMap in LogRecord

[cijothomas]

Changes

LogRecord's body, attributes supported AnyValue, and was using OrderMap (custom Struct internally using IndexMap). This PR modified it to use regular HashMap as there is no requirement to maintain order.

This achieves 2 things:

1. Slight boost in perf.
2. Avoids IndexMap dependency. - SpanAttributes modified to use Vec instead of OrderMap/EvictedHashMap #1293 had already removed the usage of this for Span attributes, and this PR removed the remaining usage, allowing us to drop the dependency.

Benchmark code:

fn insert_indexmap(c: &mut Criterion) {
    c.bench_function("Insert into IndexMap", |b| {
        b.iter(|| {
            let mut map = IndexMap::new();
            for i in 0..1000 {
                map.insert(i, i);
            }
        });
    });
}

fn insert_hashmap(c: &mut Criterion) {
    c.bench_function("Insert into HashMap", |b| {
        b.iter(|| {
            let mut map = HashMap::new();
            for i in 0..1000 {
                map.insert(i, i);
            }
        });
    });
}

Insert into IndexMap time: [21.337 µs 21.578 µs 21.843 µs]
Insert into HashMap time: [13.573 µs 13.743 µs 13.939 µs]

Merge requirement checklist

• CONTRIBUTING guidelines followed
• Unit tests added/updated (if applicable)
• Appropriate CHANGELOG.md files updated for non-trivial, user-facing changes
• Changes in public API reviewed (if applicable)

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Files	Coverage Δ
opentelemetry-prometheus/src/utils.rs	100.0% <100.0%> (ø)
opentelemetry/src/lib.rs	100.0% <ø> (ø)
opentelemetry/src/trace/mod.rs	86.3% <ø> (ø)
opentelemetry/src/logs/record.rs	0.0% <0.0%> (ø)

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