[CAL][8] - rename LegacyAccessor to CRCWAccesor and update contract writer mock

[ogtownsend]

core ref: 3ca064e5c3ae55fbfbe012b14f6e8e8ac9351143

• Fast follow to this comment: [CAL][1] - Add initial CAL scaffolding to CCIPReader with legacy accessor #978 (comment)

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] - rename LegacyAccessor to CRCWAccesor and update contract writer mock #993

[github-actions]

Metric	ogt/cal-8-rename-LegacyAccessor-and-update-contract-writer-mock	ogt/cal-7-implement-GetExpectedNextSequenceNumber
Coverage	71.9%	71.5%

[winder]

nit: I like the name "GenericAccessor" slightly more than CRCWAccessor because we could have multiple accessors implemented with CR/CW. But up to you if you like this better.

The base branch was changed.