## Review after #16059
**What type of PR is this?**
Feature
**What does this PR do?**
This PR introduces logrus writer hooks into the logging of prysm.
when log-format is text:
- set the default logrus output to be `io.Discard`
- create a writer hook for terminal, with formatting and coloring
enabled.
- create a separate writer hook for log-file (if enabled), without
coloring.
This immediately allows for having formatted/colored terminal logs,
while keeping the log-file clean.
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