refactor: RAV struct timestamp to timestamp_ns

[aasseman]

Renaming timestamp to timestamp_ns in the RAV struct.

Note: It's better not to wait too long for these kinds of changes, because naming schemes trickle all the way down to the JSON-RPC API.

[github-actions[bot]]

Coverage after merging rav_struct_timestamp_ns into main will be

92.08%

Coverage Report

File	Stmts	Branches	Funcs	Lines	Uncovered Lines
tap_core/src
eip_712_signed_message.rs	64.10%	100%	44.44%	70%	41, 52
lib.rs	96.49%	100%	86.67%	97.98%
receipt_aggregate_voucher.rs	81.58%	100%	57.14%	87.10%	21
tap_core/src/adapters/test
collateral_adapter_mock.rs	82.98%	100%	71.43%	85%	25–26, 44, 50–52
collateral_adapter_test.rs	100%	100%	100%	100%
rav_storage_adapter_mock.rs	94.74%	100%	83.33%	96.88%	7
rav_storage_adapter_test.rs	100%	100%	100%	100%
receipt_checks_adapter_mock.rs	87.18%	100%	83.33%	87.88%	49, 53–55
receipt_checks_adapter_test.rs	100%	100%	100%	100%
receipt_storage_adapter_mock.rs	97.37%	100%	92.31%	98.41%	7
receipt_storage_adapter_test.rs	100%	100%	100%	100%
tap_core/src/tap_receipt
mod.rs	75%	100%	57.14%	82.35%
receipt.rs	67.65%	100%	55.56%	72%	20, 44
received_receipt.rs	82.42%	100%	75.86%	83.82%	100–102, 109–111, 113–115, 160, 171, 185–187, 95–97

[ColePBryan]

I thought they were all updated. Not sure how this one slipped by.

[aasseman]

Rebased onto latest main

[github-actions[bot]]

Coverage after merging rav_struct_timestamp_ns into main will be

86.37%

Coverage Report

File	Stmts	Branches	Funcs	Lines	Uncovered Lines
tap_core/src
eip_712_signed_message.rs	67.74%	100%	55.56%	72.73%	49
lib.rs	71.43%	100%	71.43%	71.43%	17
receipt_aggregate_voucher.rs	81.58%	100%	57.14%	87.10%	21
tap_core/src/adapters/test
collateral_adapter_mock.rs	82.98%	100%	71.43%	85%	25–26, 44, 50–52
collateral_adapter_test.rs	100%	100%	100%	100%
rav_storage_adapter_mock.rs	94.74%	100%	83.33%	96.88%	7
rav_storage_adapter_test.rs	100%	100%	100%	100%
receipt_checks_adapter_mock.rs	87.18%	100%	83.33%	87.88%	49, 53–55
receipt_checks_adapter_test.rs	95.83%	100%	100%	95%	53
receipt_storage_adapter_mock.rs	97.37%	100%	92.31%	98.41%	7
receipt_storage_adapter_test.rs	100%	100%	100%	100%
tap_core/src/tap_receipt
mod.rs	66.67%	100%	50%	75%
receipt.rs	67.65%	100%	55.56%	72%	20, 44
received_receipt.rs	82.42%	100%	75.86%	83.82%	100–102, 109–111, 113–115, 160, 171, 185–187, 95–97