Add agent config option to set NGINX API URL #6711

Job	Run time
Component Tests	1m 3s
Performance Tests	7m 49s
Lint	1m 1s
Unit Tests	3m 44s
Build signed snapshot	7m 25s
Build unsigned snapshot	4m 29s
Build Grafana Dashboard Example	1m 27s
Integration Tests - Official Plus Images (debian, bookworm, r31, debian, /nginx-plus/agent)	4m 1s
Integration Tests - Official OSS Images (alpine, stable, alpine)	3m 31s
Integration Tests - Official Plus Images (alpine, 3.20, r32, alpine, /nginx-plus/agent)	4m 1s
Integration Tests - Official OSS Images (alpine, mainline, alpine)	3m 26s
Integration Tests - Official OSS Images (bookworm, mainline, debian)	3m 41s
Integration Tests - Official Plus Images (debian, bookworm, r32, debian, /nginx-plus/agent)	4m 13s
Integration Tests - Official OSS Images (bookworm, stable, debian)	3m 37s
Integration Tests (rockylinux, 9)	4m 57s
Integration Tests (oraclelinux, 8)	6m 10s
Integration Tests (rockylinux, 8)	5m 20s
Integration Tests (almalinux, 8)	4m 57s
Integration Tests (alpine, 3.21)	3m 45s
Integration Tests (ubuntu, 24.04)	4m 20s
Integration Tests (alpine, 3.20)	3m 54s
Integration Tests (amazonlinux, 2)	5m 16s
Integration Tests (almalinux, 9)	4m 45s
Integration Tests (oraclelinux, 9)	5m 7s
Integration Tests (amazonlinux, 2023)	5m 3s
Integration Tests (debian, bullseye-slim)	4m 34s
Integration Tests (alpine, 3.23)	3m 52s
Integration Tests (debian, bookworm-slim)	4m 27s
Integration Tests (alpine, 3.22)	3m 56s
	2h 3m 51s

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