DOC-14144 Product Change- PR #148525 - pkg/util/log: add otlp log sink (#20320)

- In configure-logs.md, (a) added sections for Output to OTLP-compatible network collectors and Set OTLP defaults (b) updated default log config.
- In logging-use-cases.md, modified example for Network logging with log buffering to use OTLP instead of Fluentd.

* Incorporated Rich’s feedback.

Author: florence-crl