Add agent config option to set NGINX API URL #6707

Job	Run time
Build unsigned snapshot	5m 18s
Lint	1m 0s
Build signed snapshot	8m 6s
Unit Tests	3m 49s
Component Tests	1m 0s
Performance Tests	7m 42s
Build Grafana Dashboard Example	1m 37s
Integration Tests - Official Plus Images (debian, bookworm, r32, debian, /nginx-plus/agent)	4m 9s
Integration Tests - Official OSS Images (bookworm, mainline, debian)	3m 40s
Integration Tests - Official Plus Images (alpine, 3.20, r32, alpine, /nginx-plus/agent)	4m 5s
Integration Tests - Official OSS Images (alpine, mainline, alpine)	3m 25s
Integration Tests - Official Plus Images (debian, bookworm, r31, debian, /nginx-plus/agent)	4m 9s
Integration Tests - Official OSS Images (alpine, stable, alpine)	3m 40s
Integration Tests - Official OSS Images (bookworm, stable, debian)	3m 39s
Integration Tests (ubuntu, 24.04)	4m 38s
Integration Tests (alpine, 3.20)	3m 48s
Integration Tests (oraclelinux, 8)	6m 12s
Integration Tests (debian, bullseye-slim)	4m 38s
Integration Tests (debian, bookworm-slim)	4m 28s
Integration Tests (alpine, 3.23)	3m 42s
Integration Tests (alpine, 3.21)	3m 59s
Integration Tests (oraclelinux, 9)	5m 18s
Integration Tests (rockylinux, 9)	4m 56s
Integration Tests (amazonlinux, 2)	5m 43s
Integration Tests (rockylinux, 8)	5m 15s
Integration Tests (almalinux, 8)	12m 17s
Integration Tests (alpine, 3.22)	3m 41s
Integration Tests (amazonlinux, 2023)	4m 55s
Integration Tests (almalinux, 9)	4m 27s
	2h 13m 16s

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