feat: Provide Azure Resource Graph rate limiting info & throttling status metrics

[tomkerkhove]

Provide Azure Resource Graph rate limiting info & throttling status metrics

• Implement scraper
• Implement resource discovery
• Provide unit tests
• Test end-to-end
• Document scraper
• Add entry to changelog

Scraper output:

# HELP promitor_ratelimit_arm Indication how many calls are still available before Azure Resource Manager (ARM) is going to throttle us.
# TYPE promitor_ratelimit_arm gauge
promitor_ratelimit_arm{tenant_id="c8819874-9e56-4e3f-b1a8-1c0325138f27",subscription_id="0329dd2a-59dc-4493-aa54-cb01cb027dc2",app_id="ceb249a3-44ce-4c90-8863-6776336f5b7e"} 11995 1629719527020
promitor_ratelimit_arm{tenant_id="c8819874-9e56-4e3f-b1a8-1c0325138f27",subscription_id="0f9d7fea-99e8-4768-8672-06a28514f77e",app_id="ceb249a3-44ce-4c90-8863-6776336f5b7e"} 11989 1629719532626
# HELP promitor_ratelimit_arm_throttled Indication concerning Azure Resource Manager are being throttled. (1 = yes, 0 = no).
# TYPE promitor_ratelimit_arm_throttled gauge
promitor_ratelimit_arm_throttled{tenant_id="c8819874-9e56-4e3f-b1a8-1c0325138f27",subscription_id="0329dd2a-59dc-4493-aa54-cb01cb027dc2",app_id="ceb249a3-44ce-4c90-8863-6776336f5b7e"} 0 1629719527020
promitor_ratelimit_arm_throttled{tenant_id="c8819874-9e56-4e3f-b1a8-1c0325138f27",subscription_id="0f9d7fea-99e8-4768-8672-06a28514f77e",app_id="ceb249a3-44ce-4c90-8863-6776336f5b7e"} 0 1629719532626

Discovery output:

# HELP promitor_ratelimit_resource_graph_remaining Indication how many calls are still available before Azure Resource Graph is going to throttle us.
# TYPE promitor_ratelimit_resource_graph_remaining gauge
promitor_ratelimit_resource_graph_remaining{tenant_id="c8819874-9e56-4e3f-b1a8-1c0325138f27",cloud="Global",auth_mode="ServicePrincipal",app_id="67882a00-21d3-4ee7-b32a-430ea0768cd3"} 9 1629719863738
# HELP promitor_ratelimit_resource_graph_throttled Indication concerning Azure Resource Graph are being throttled. (1 = yes, 0 = no).
# TYPE promitor_ratelimit_resource_graph_throttled gauge
promitor_ratelimit_resource_graph_throttled{tenant_id="c8819874-9e56-4e3f-b1a8-1c0325138f27",cloud="Global",auth_mode="ServicePrincipal",app_id="67882a00-21d3-4ee7-b32a-430ea0768cd3"} 0 1629719863738

Fixes #973
Fixes #1171
Fixes #1739
Fixes #1738