Updates to RecordDataHeader

[TedHartMS]

This pull request updates the codebase to use the DataHeader property instead of the Info and RecordDataHeader properties for accessing metadata on log records. This change improves consistency and prepares the code for future enhancements by centralizing metadata access. Additionally, it updates documentation and value range logic for value overflow thresholds.

Key changes include:

Refactoring to use DataHeader:

• Make RecordDataHeader fixed 16 bytes, with keys and values fixed at 12 and 22 bits respectively for length, instead of variable-bytelen. Anything over this becomes overflow.

• Replaced all usages of logRecord.Info and logRecord.RecordDataHeader with logRecord.DataHeader for properties like ValueIsObject, HasExpiration, HasETag, ValueIsInline, and RecordType throughout the codebase, including in expiration checks, type checks, and record management logic. [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17]

Documentation and configuration updates:

• Updated comments and logic in GarnetServerOptions.cs to clarify and adjust the allowed value range for ValueOverflowThresholdBytes, now using a direct value with new min/max constants.

Other codebase updates:

• Removed unnecessary clearing of ETag in InitialDeleter, likely because the new DataHeader abstraction handles this elsewhere.

These updates should make metadata handling more robust and less error-prone by consolidating access patterns.

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[badrishc]

Can we have inline thresholds more like this: 1 KB keys (10 bits) + 16 MB values (24 bits) = 34 bits