[CAL][1] - Add initial CAL scaffolding to CCIPReader with legacy accessor

[ogtownsend]

core ref: 7404f6349ac2bdb222f3c5889669d98760920168

• Add initial support for the chain accessor to ccip.go (CCIPReader)
• Merging the skeleton with the outlined and unimplemented functions should allow us to more easily chip away at the migration from CCIPReader --> CR/CW to CCIPReader --> CAL on a per-function basis.
• Taking this approach where we can test incrementally should ideally be less risky than a single PR where all functions are migrated at once
• For more context, see NONEVM-1865

Stack:

1. ➡ [CAL][1] - Add initial CAL scaffolding to CCIPReader with legacy accessor #978
2. [CAL][2] - Implement Metadata() and GetContractAddress() #980
3. [CAL][3] - Implement GetChainFeeComponents #985
4. [CAL][4] - Implement MsgsBetweenSeqNums() function in accessor #987
5. [CAL][5] - implement LatestMsgSeqNum #988
6. [CAL][6] - move SourceChainConfig to chainaccessor types #989
7. [CAL][7] - implement GetExpectedNextSequenceNumber #990
8. [CAL][8] - Some minor cleanup and renaming #999
9. [CAL][9] - Implement CommitReportsGTETimestamp, GetTokenPriceUSD, and GetLatestPriceSeqNr #1000
10. [CAL][10] - Implement Nonces and GetChainFeePriceUpdate #1014
11. [CAL][11] - Implement ExecutedMessages for chain accessor #1017

[github-actions]

Metric	ogt/cal-initial-scaffolding-in-ccip-reader	main
Coverage	72.3%	72.1%

[winder]

I made two suggestions that I think you should take, but they can be implemented as followups.