feat(cli): log warning if otlp feature is not enabled

[shekhirin]

Addresses two issues:

1. OTLP initialization log wasn't printed to stdout, because trace layers initialization happened after we emitted that log.
2. When OTLP tracing arguments were provided but feature is not enabled, we silently didn't initialize the layer.

Additionally, deduplicates the OTLP tracing initialization logic between reth-ethereum-cli and reth-optimism-cli crates.

Demonstration

❯ cargo r --no-default-features --quiet node --chain hoodi --tracing-otlp
2025-11-11T16:03:09.066553Z  INFO Initialized tracing, debug log directory: /Users/shekhirin/Library/Caches/reth/logs/hoodi
2025-11-11T16:03:09.066680Z  WARN Provided OTLP tracing arguments do not have effect, compile with the `otlp` feature

❯ cargo r --quiet node --chain hoodi --tracing-otlp
2025-11-11T16:03:37.324707Z  INFO Initialized tracing, debug log directory: /Users/shekhirin/Library/Caches/reth/logs/hoodi
2025-11-11T16:03:37.324869Z  INFO Started OTLP Http tracing export to http://localhost:4318/v1/traces

[codspeed-hq]

CodSpeed Performance Report

Merging #19648 will not alter performance

_{Comparing alexey/otlp-tracing-logs (ce7e789) with main (3a672ee)}

Summary

✅ 81 untouched

[Rjected]

very nice

[lean-apple]

Thanks @shekhirin for the refactor to avoid the duplication of code !