Update indexed fields in Portal events

[0xIryna]

Proposed changes

• index sender, recipient and destinationChainId in MTokenSent event.
• index sender, recipient and sourceChainId in MTokenReceive event
• index listName, account and destinationChainId in RegistrarListStatusSent event
• remove TODO comments that no longer apply

Motivation

While it's unclear how Portal events will be used off-chain, it's more likely to search and filter events by sender, recipient and chainId, rather than messageId, which is unique per message.

[github-actions]

LCOV of commit a7da286 during Forge Coverage #47

Summary coverage rate:
  lines......: 99.2% (128 of 129 lines)
  functions..: 94.9% (37 of 39 functions)
  branches...: 85.7% (18 of 21 branches)

Files changed coverage rate:
                             |Lines       |Functions  |Branches    
  Filename                   |Rate     Num|Rate    Num|Rate     Num
  =================================================================
  src/Portal.sol             | 100%     24|80.0%    10|80.0%      5

[github-actions]

Changes to gas cost

Generated at commit: 408678bb92f15333f8eba2ba5a918cdf6e93a100, compared to commit: 151a6649688b7342065f1156fe36fd380fb1d03d

🧾 Summary (20% most significant diffs)

Contract	Method	Avg (+/-)	%
SpokePortal	attestationReceived	+290 ❌	+0.24%
HubPortal	sendRegistrarListStatus	+116 ❌	+0.17%

---

Full diff report 👇

Contract	Deployment Cost (+/-)	Method	Min (+/-)	%	Avg (+/-)	%	Median (+/-)	%	Max (+/-)	%	# Calls (+/-)
SpokePortal	5,170,910 (-695)	attestationReceived transfer	55,382 (0) 136,929 (+104)	0.00% +0.08%	120,818 (+290) 136,929 (+104)	+0.24% +0.08%	117,041 (+121) 136,929 (+104)	+0.10% +0.08%	142,899 (+125) 136,929 (+104)	+0.09% +0.08%	520 (0) 1 (0)
HubPortal	5,625,918 (+240)	attestationReceived sendMTokenIndex sendRegistrarListStatus transfer	96,364 (+121) 72,090 (-110) 70,267 (+116) 136,874 (+104)	+0.13% -0.15% +0.17% +0.08%	110,508 (+106) 72,090 (-110) 70,267 (+116) 136,874 (+104)	+0.10% -0.15% +0.17% +0.08%	97,014 (+122) 72,090 (-110) 70,267 (+116) 136,874 (+104)	+0.13% -0.15% +0.17% +0.08%	125,685 (+125) 72,090 (-110) 70,267 (+116) 136,874 (+104)	+0.10% -0.15% +0.17% +0.08%	515 (0) 1 (0) 1 (0) 1 (0)