[Breaking] Use non-delta codec for oneof type (#146)

Resolves #127

This simplifies oneof codec and improves codec speed at the cost of slight increase
of uncompressed size. The zstd-compressed size is approximately the same (slightly
increased or decresed depending on the dataset).

### Benchmarks

Otel schema speed improvement:
```
                                  │ bench_base.txt │         bench_current.txt         │
                                  │   sec/point    │  sec/point   vs base              │
SerializeNative/STEF/serialize-10      64.36n ± 1%   63.10n ± 2%  -1.96% (p=0.020 n=9)
DeserializeNative/STEF/deser-10        24.06n ± 1%   22.70n ± 1%  -5.65% (p=0.000 n=9)
geomean                                39.35n        37.85n       -3.82%
```

Otel schema size before the change:
```
File                           Uncompressed   Zstd Bytes
hipstershop-otelmetrics.stefz        432716        93702
hostandcollector-otelmetrics.stefz      1258652        83009
astronomy-otelmetrics.stefz         7462303      1652082
```

After the change:
```
File                           Uncompressed   Zstd Bytes
hipstershop-otelmetrics.stefz        441558        95083
hostandcollector-otelmetrics.stefz      1266627        79835
astronomy-otelmetrics.stefz         7557122      1644464
```

Author: tigrannajaryan

.github/workflows/benchmark.yml

@@ -85,7 +85,7 @@ jobs:
           HEAD=$(git rev-parse HEAD)
           git reset --hard ${{ github.event.pull_request.base.sha }}
           export REF_NAME=main
-          cd benchmarks && make bench-run bench-stat
+          cd benchmarks && make gentestfiles bench-run bench-stat
           git reset --hard $HEAD
 
       - name: Benchmark stats

benchmarks/scripts/genoldtestfiles.sh

@@ -14,7 +14,7 @@ TMPDIR=$(mktemp -d)
 cp ./gentestfiles.sh "$TMPDIR/"
 
 # Checkout the base branch to compare to
-BASE_BRANCH=21f498a293dbdf6e29c75385ba0043dc0f5e4009
+BASE_BRANCH=tigran/oneofcodec # Change this to the main branch commit after tigran/oneofcodec is merged.
 git -c advice.detachedHead=false checkout $BASE_BRANCH
 
 # Convert/generate the files.