Add more metrics to the UDP tracker stats

[josecelano]

Add more metrics to the UDP tracker stats. The new values are:

• udp4_requests: total number of requests received from IPv4 clients.
• udp6_requests: total number of requests received from IPv6 clients.
• udp4_responses: total number of responses sent to IPv4 clients.
• udp6_responses: total number of responses sent to IPv6 clients.
• udp_requests_aborted: total number of requests aborted to make room in the active requests buffer.

Notes

• Responses sent might differ from requests received because of aborted requests.
• When we merge the IP ban service, we can add a new metric for the total number of IPs banned.
• I want to add these new metrics to the live demo Grafana dashboard.

Subtasks

• udp4_requests
• udp6_requests
• udp4_responses
• udp6_responses
• udp_requests_aborted
• Benchmarking to check how it affects performance before merging it.

[codecov]

Codecov Report

Attention: Patch coverage is 68.18182% with 28 lines in your changes missing coverage. Please review.

Project coverage is 75.81%. Comparing base (20639e8) to head (6ca82e9).

Files with missing lines	Patch %	Lines
src/core/statistics.rs	40.00%	18 Missing ⚠️
src/servers/apis/v1/context/stats/responses.rs	0.00%	9 Missing ⚠️
src/servers/udp/server/request_buffer.rs	80.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1130      +/-   ##
===========================================
- Coverage    75.91%   75.81%   -0.11%     
===========================================
  Files          168      168              
  Lines        11369    11437      +68     
  Branches     11369    11437      +68     
===========================================
+ Hits          8631     8671      +40     
- Misses        2573     2601      +28     
  Partials       165      165              

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[josecelano]

Benchmarking results

Best

Requests out: 475899.12/second
Responses in: 384068.37/second
  - Connect responses:  189932.78
  - Announce responses: 190331.68
  - Scrape responses:   3803.91
  - Error responses:    0.00
Peers per announce response: 0.00
Announce responses per info hash:
  - p10: 1
  - p25: 1
  - p50: 1
  - p75: 1
  - p90: 2
  - p95: 3
  - p99: 105
  - p99.9: 311
  - p100: 381

Worst

Requests out: 397401.29/second
Responses in: 366317.14/second
  - Connect responses:  181306.70
  - Announce responses: 181435.14
  - Scrape responses:   3575.29
  - Error responses:    0.00
Peers per announce response: 0.00
Announce responses per info hash:
  - p10: 1
  - p25: 1
  - p50: 1
  - p75: 1
  - p90: 2
  - p95: 3
  - p99: 104
  - p99.9: 295
  - p100: 377

[josecelano]

ACK 6ca82e9