feat: improve grpc get_balance response

[hansieodendaal]

Description

• Improved the wallet grpc method get_balance response by implementing an event-driven balance cache update. All events that could change the balance are monitored and consecutive calls to the wallet backend are only made when the balance changed.
• Cleaned up unused events (events that were monitored somewhere but never set) in pub enum TransactionEvent.
• Added a missing shutdown signal to grpc method async fn stream_transaction_events in the wallet grpc server.

Closes #6754

Motivation and Context

When calling the wallet grpc method get_balance repeatedly and quickly in succession on wallets with many outputs, resources are wasted in the wallet when nothing changes, and the client experiences unnecessary long response times.

How Has This Been Tested?

System-level testing on a large wallet with an external grpc client. See logs with response times below.

[wallet::ui::grpc::get_balance_debounced] TRACE start_event_monitor
[wallet::ui::grpc::get_balance_debounced] TRACE is_refresh_needed 'true'
[wallet::ui::grpc::get_balance_debounced] TRACE set_refresh_needed 'false'
[wallet::ui::grpc] TRACE 'get_balance' completed in 172.28ms
[wallet::ui::grpc::get_balance_debounced] TRACE is_refresh_needed 'false'
[wallet::ui::grpc] TRACE 'get_balance' completed in 29.40µs
[wallet::ui::grpc::get_balance_debounced] TRACE is_refresh_needed 'false'
[wallet::ui::grpc] TRACE 'get_balance' completed in 36.00µs
[wallet::ui::grpc::get_balance_debounced] TRACE is_refresh_needed 'false'
[wallet::ui::grpc] TRACE 'get_balance' completed in 26.40µs
[wallet::ui::grpc::get_balance_debounced] TRACE set_refresh_needed 'true'
[wallet::ui::grpc::get_balance_debounced] TRACE is_refresh_needed 'true'
[wallet::ui::grpc::get_balance_debounced] TRACE set_refresh_needed 'false'
[wallet::ui::grpc] TRACE 'get_balance' completed in 145.39ms
[wallet::ui::grpc::get_balance_debounced] TRACE is_refresh_needed 'false'
[wallet::ui::grpc] TRACE 'get_balance' completed in 22.00µs
[wallet::ui::grpc::get_balance_debounced] TRACE is_refresh_needed 'false'
[wallet::ui::grpc] TRACE 'get_balance' completed in 33.70µs
[wallet::ui::grpc::get_balance_debounced] TRACE is_refresh_needed 'false'
[wallet::ui::grpc] TRACE 'get_balance' completed in 25.40µs
[wallet::ui::grpc::get_balance_debounced] TRACE set_refresh_needed 'true'
[wallet::ui::grpc::get_balance_debounced] TRACE is_refresh_needed 'true'
[wallet::ui::grpc::get_balance_debounced] TRACE set_refresh_needed 'false'
[wallet::ui::grpc] TRACE 'get_balance' completed in 156.75ms
[wallet::ui::grpc::get_balance_debounced] TRACE is_refresh_needed 'false'
[wallet::ui::grpc] TRACE 'get_balance' completed in 35.70µs
[wallet::ui::grpc::get_balance_debounced] TRACE is_refresh_needed 'false'
[wallet::ui::grpc] TRACE 'get_balance' completed in 23.40µs

What process can a PR reviewer use to test or verify this change?

System-level testing with an external grpc client.

Breaking Changes

• None
• Requires data directory on base node to be deleted
• Requires hard fork
• Other - Please specify

[github-actions]

Test Results (CI)

    3 files    129 suites   36m 40s ⏱️
1 350 tests 1 350 ✅ 0 💤 0 ❌
4 048 runs  4 048 ✅ 0 💤 0 ❌

Results for commit 97cad31.

[github-actions]

Test Results (Integration tests)

 2 files  + 2  11 suites  +11   38m 49s ⏱️ + 38m 49s
36 tests +36  35 ✅ +35  0 💤 ±0  1 ❌ +1 
38 runs  +38  36 ✅ +36  0 💤 ±0  2 ❌ +2 

For more details on these failures, see this check.

Results for commit 97cad31. ± Comparison against base commit f0cf697.

[SWvheerden]

just one question