Implement HEXPIREAT command

[kelvinmwinuka]

Sets the exact expiration time from now, in seconds, of a field in a hash.
Reference: https://redis.io/docs/latest/commands/hexpireat/

Client-Server Spec:

Command File: ./internal/modules/hash/commands.go
Test File: ./internal/modules/hash/commands_test.go

Command: hexpireat
Module: constants.HashModule
Categories: contants.HashCategory, constants.WriteCategory, constants.FastCategory
Description: (HEXPIREAT key unix-time-seconds [NX | XX | GT | LT] FIELDS numfields field [field ...]) Sets the exact expiration time from now of a field in a hash.
Sync: true

NOTE: You may need to change the internal representation of the hash to hold a more complex data type that includes the field's value and expiry time instead of just the value. If the representation is already changed from a previous implementation, then use the current implementation.

Embedded Spec:

Command File: ./echovault/api_hash.go
Test File: ./echovault/api_hash_test.go

Documentation

Add documentation to ./docs/docs/commands/hash/HEXPIREAT.mdx