represent share work as u64 (where appropriate)

[plebhash]

close #2092

companion stratum-mining/sv2-apps#449

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client side

work acknowledged by upstream arrives over the wire as u64 (SubmitSharesSuccess.new_shares_sum), but for auditability we now track two values:

• acknowledged_work_sum (u64): what upstream acknowledged over SV2 messages
• validated_work_sum (f64): what the client validated locally (tracked by job difficulty)

this keeps wire accounting aligned with protocol types, while still allowing client to detect mismatches between what it validated vs what server acknowledged

server side

if we truncated every share's work into u64 before storing it in memory, repeated truncation would cause accumulated accounting drift over time

so on the server side, truncation stays limited to get_last_batch_work_sum (used for crafting SubmitSharesSuccess), while in-memory work accounting remains f64

[plebhash]

reverting back to draft, see: #2092 (comment)

[plebhash]

reverting back to draft, see: #2092 (comment)

adapted to the new direction

now client side keeps track of acknowledged_work_sum: u64 vs validated_work_sum: f64

server side only truncates on get_last_batch_work_sum for the creation of SubmitSharesSuccess message

[GitGab19]

LGTM