[border-router] introduce br_log for logging helpers

[abtink]

This change introduces new files br_log.cpp and br_log.hpp to house common logging helper functions for the border router modules.

Helper functions for logging Router Advertisement (RA) headers, Prefix Information Options (PIO), Route Information Options (RIO), and other related options are moved into this new module.

The log module name is also updated from RoutingManager to a more general BorderRouting.

This change improves code structure by decoupling logging functionalities from the RoutingManager.

[github-actions]

Merging #11998 into main

name	branch	text	data	bss	total
ot-cli-ftd	cfd1d08	479928	860	66580	547368
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ot-ncp-ftd	cfd1d08	446332	764	61824	508920
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ot-cli-mtd	cfd1d08	372560	764	51052	424376
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ot-ncp-mtd	cfd1d08	353612	764	46320	400696
	e5dc905	353612	764	46320	400696
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ot-cli-ftd-br	cfd1d08	582592	868	136404	719864
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ot-rcp	cfd1d08	63136	568	20804	84508
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Library files

name	branch	text	data	bss	total
libopenthread-ftd.a	cfd1d08	247024	95	40358	287477
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libopenthread-cli-ftd.a	cfd1d08	61027	0	8083	69110
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libopenthread-ncp-ftd.a	cfd1d08	33581	0	5948	39529
	e5dc905	33581	0	5948	39529
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libopenthread-mtd.a	cfd1d08	165305	0	24854	190159
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libopenthread-cli-mtd.a	cfd1d08	41251	0	8059	49310
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libopenthread-ncp-mtd.a	cfd1d08	25805	0	5948	31753
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libopenthread-ftd-br.a	cfd1d08	350987	100	110150	461237
	e5dc905	351000	100	110150	461250
	+/-	+13	+0	+0	+13
libopenthread-cli-ftd-br.a	cfd1d08	78917	0	8115	87032
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libopenthread-rcp.a	cfd1d08	9944	0	5060	15004
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libopenthread-radio.a	cfd1d08	19411	0	238	19649
	e5dc905	19411	0	238	19649
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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.37%. Comparing base (cfd1d08) to head (737c9dd).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #11998      +/-   ##
==========================================
+ Coverage   70.59%   76.37%   +5.78%     
==========================================
  Files         659      645      -14     
  Lines      102307    95417    -6890     
==========================================
+ Hits        72222    72876     +654     
+ Misses      30085    22541    -7544     

Files with missing lines	Coverage Δ
src/core/border_router/br_log.cpp	100.00% <100.00%> (ø)
src/core/border_router/br_log.hpp	100.00% <100.00%> (ø)
src/core/border_router/routing_manager.cpp	89.33% <ø> (-3.24%)	⬇️
src/core/border_router/routing_manager.hpp	80.32% <ø> (-9.19%)	⬇️

... and 358 files with indirect coverage changes

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[abtink]

/gemini review

[gemini-code-assist]

Code Review

This pull request is a nice refactoring that moves logging helper functions into a new br_log module, improving code organization and decoupling logging from the RoutingManager. The log module name is also appropriately updated to the more general BorderRouting. The changes are well-structured and clear. I have a couple of minor suggestions for the new br_log.cpp file to further improve the code.

[Irving-cl]

LGTM 👍

[Copilot]

Pull Request Overview

This PR introduces a new logging module br_log to house common Border Router logging helper functions. The change extracts logging functions from RoutingManager into dedicated files, improving code modularity and organization.

• Moved logging functions for RA headers, PIO, RIO, and RDNSS options from RoutingManager to new br_log module
• Updated log module name from "RoutingManager" to "BorderRouting" for broader scope
• Added new source files br_log.cpp and br_log.hpp with proper build system integration

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/core/border_router/routing_manager.hpp	Removed logging function declarations from RoutingManager class
src/core/border_router/routing_manager.cpp	Removed logging function implementations and updated log module name
src/core/border_router/br_log.hpp	New header file with logging function declarations and documentation
src/core/border_router/br_log.cpp	New implementation file with extracted logging functions
src/core/CMakeLists.txt	Added br_log.cpp to build configuration
src/core/BUILD.gn	Added br_log source files to build configuration

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