refactor: Reorganize RPC handler files

[mvadari]

High Level Overview of Change

This PR:

• Ensures that each RPC has its own handler .cpp file, to make them easier to find
• Splits up the RPCs into subfolders, using https://xrpl.org/docs/references/http-websocket-apis/public-api-methods and https://xrpl.org/docs/references/http-websocket-apis/admin-api-methods for reference on how to divide them up

There is no functionality or source code change, only moving code around and renaming files/headers.

Context of Change

Making the repo easier to manage/traverse

API Impact

N/A

[codecov]

Codecov Report

❌ Patch coverage is 75.17241% with 36 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.4%. Comparing base (0eedefb) to head (4abf6c9).
⚠️ Report is 17 commits behind head on develop.

Files with missing lines	Patch %	Lines
...ld/rpc/handlers/admin/peer/PeerReservationsDel.cpp	0.0%	15 Missing ⚠️
...d/rpc/handlers/admin/peer/PeerReservationsList.cpp	0.0%	7 Missing ⚠️
src/xrpld/rpc/handlers/ChannelVerify.cpp	83.9%	5 Missing ⚠️
src/xrpld/rpc/handlers/account/AccountNFTs.cpp	93.0%	5 Missing ⚠️
src/xrpld/rpc/handlers/orderbook/NFTBuyOffers.cpp	71.4%	2 Missing ⚠️
src/xrpld/rpc/handlers/orderbook/NFTSellOffers.cpp	71.4%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           develop   #6628   +/-   ##
=======================================
  Coverage     81.4%   81.4%           
=======================================
  Files          997    1004    +7     
  Lines        74410   74410           
  Branches      7562    7556    -6     
=======================================
+ Hits         60598   60606    +8     
+ Misses       13812   13804    -8     

Files with missing lines	Coverage Δ
src/xrpld/overlay/detail/OverlayImpl.cpp	32.9% <ø> (ø)
src/xrpld/rpc/detail/Handler.cpp	88.1% <ø> (ø)
src/xrpld/rpc/handlers/account/AccountChannels.cpp	81.4% <ø> (ø)
...c/xrpld/rpc/handlers/account/AccountCurrencies.cpp	97.5% <ø> (ø)
src/xrpld/rpc/handlers/account/AccountInfo.cpp	85.4% <ø> (ø)
src/xrpld/rpc/handlers/account/AccountLines.cpp	91.2% <ø> (ø)
src/xrpld/rpc/handlers/account/AccountObjects.cpp	95.6% <ø> (ø)
src/xrpld/rpc/handlers/account/AccountOffers.cpp	89.5% <ø> (ø)
src/xrpld/rpc/handlers/account/AccountTx.cpp	86.8% <100.0%> (ø)
src/xrpld/rpc/handlers/account/GatewayBalances.cpp	89.4% <ø> (ø)
... and 66 more

... and 5 files with indirect coverage changes

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[Tapanito]

/ai-review

[xrplf-ai-reviewer]

Ship it

Review by Claude Opus 4.6 · Prompt: V12

[Tapanito]

Nice, clean reorganisation. LGTM.

[github-actions]

This PR has conflicts, please resolve them in order for the PR to be reviewed.