[Access] Add scheduled transactions endpoints

[peterargue]

Initial implementation of the scheduled transactions index and endpoints.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 4.88656% with 545 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
access/unimplemented.go	0.00%	115 Missing ⚠️
utils/unittest/fixtures/event_pending_execution.go	0.00%	103 Missing ⚠️
storage/mock/scheduled_transactions.go	0.00%	62 Missing ⚠️
storage/mock/scheduled_transactions_reader.go	0.00%	50 Missing ⚠️
storage/store/scheduled_transactions.go	0.00%	48 Missing ⚠️
access/mock/api.go	0.00%	44 Missing ⚠️
access/mock/transactions_api.go	0.00%	44 Missing ⚠️
cmd/observer/node_builder/observer_builder.go	0.00%	25 Missing ⚠️
cmd/access/node_builder/access_node_builder.go	0.00%	20 Missing ⚠️
utils/unittest/fixtures/transaction_result.go	0.00%	14 Missing ⚠️
... and 4 more

📢 Thoughts on this report? Let us know!

[devbugging]

Nice.
Are we extending the implementation of "get transaction by ID" to support system transactions (scheduled transactions)?

[peterargue]

Nice. Are we extending the implementation of "get transaction by ID" to support system transactions (scheduled transactions)?

yea, updated in 2105455

[peterargue]

I'm going to break this PR down into a few parts to make it easier to review. First part is here:
#8025