This commit updates the syslog.rst documentation to:
1. Add a new "Overview" section with the syslog-overview.png diagram
2. Introduce a comprehensive "Syslog Configuration Options" chapter
3. Document the CONFIG_SYSLOG_TIMESTAMP_MS option (newly added in driver code)
- Clarify its dependency on CONFIG_SYSLOG_TIMESTAMP
- Explain its function: use millisecond (ms) precision instead of default microsecond (µs)
4. Group all syslog Kconfig options by functional role (debug level, formatting, buffer, etc.)
- Basic Debug Log Level Configuration
- Message Formatting Configuration (timestamp/metadata/visual)
- (Other categories follow the syslog system architecture)
The documentation changes align with the recent driver enhancement:
- drivers/syslog: add millisecond option for syslog timestamp formatting
- Maintain consistency between driver code and documentation
- Make syslog configuration options more discoverable for developers
Signed-off-by: chao an <anchao.archer@bytedance.com>
