[exporter/signalfxexporter] Add all HTTP client settings to the configuration

[atoulme]

Description:
Expose all HTTP client settings to the exporter configuration so they may be set in addition to the existing flags.

Link to tracking Issue:
#16807

Testing:
Unit tests all pass.

Documentation:
N/A - not sure we need to shore up those config settings explicitly as I haven't seen that done elsewhere - please advise.

[runforesight]

Foresight Summary

    
Major Impacts

TestRabbitmqIntegration ❌ failed 1 times in 10 runs (10% fail rate).

TestRabbitmqIntegration/Running_rabbitmq_3.9 ❌ failed 1 times in 10 runs (10% fail rate).

build-and-test-windows duration(5 seconds) has decreased 44 minutes 50 seconds compared to main branch avg(44 minutes 55 seconds).

View More Details

⭕  build-and-test-windows workflow has finished in 5 seconds (44 minutes 50 seconds less than main branch avg.) and finished at 26th Dec, 2022.

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Job	Failed Steps	Tests
windows-unittest-matrix	-     🔗	N/A	See Details
windows-unittest	-     🔗	N/A	See Details

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✅  tracegen workflow has finished in 1 minute (3 minutes 1 second less than main branch avg.) and finished at 26th Dec, 2022.

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Job	Failed Steps	Tests
build-dev	-     🔗	N/A	See Details
publish-latest	-     🔗	N/A	See Details
publish-stable	-     🔗	N/A	See Details

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✅  check-links workflow has finished in 1 minute 30 seconds (2 minutes 9 seconds less than main branch avg.) and finished at 26th Dec, 2022.

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Job	Failed Steps	Tests
changed files	-     🔗	N/A	See Details
check-links	-     🔗	N/A	See Details

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✅  changelog workflow has finished in 1 minute 39 seconds (6 minutes 24 seconds less than main branch avg.) and finished at 26th Dec, 2022.

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Job	Failed Steps	Tests
changelog	-     🔗	N/A	See Details

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✅  prometheus-compliance-tests workflow has finished in 3 minutes 17 seconds (6 minutes 45 seconds less than main branch avg.) and finished at 26th Dec, 2022.

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Job	Failed Steps	Tests
prometheus-compliance-tests	-     🔗	✅ 21  ❌ 0  ⏭ 0    🔗	See Details

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✅  load-tests workflow has finished in 8 minutes 6 seconds (9 minutes 16 seconds less than main branch avg.) and finished at 26th Dec, 2022.

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Job	Failed Steps	Tests
loadtest (TestIdleMode)	-     🔗	✅ 1  ❌ 0  ⏭ 0    🔗	See Details
loadtest (TestTraceAttributesProcessor)	-     🔗	✅ 3  ❌ 0  ⏭ 0    🔗	See Details
loadtest (TestTraceNoBackend10kSPS|TestTrace1kSPSWithAttrs)	-     🔗	✅ 8  ❌ 0  ⏭ 0    🔗	See Details
loadtest (TestMetric10kDPS|TestMetricsFromFile)	-     🔗	✅ 6  ❌ 0  ⏭ 0    🔗	See Details
loadtest (TestTraceBallast1kSPSWithAttrs|TestTraceBallast1kSPSAddAttrs)	-     🔗	✅ 10  ❌ 0  ⏭ 0    🔗	See Details
loadtest (TestMetricResourceProcessor|TestTrace10kSPS)	-     🔗	✅ 12  ❌ 0  ⏭ 0    🔗	See Details
loadtest (TestBallastMemory|TestLog10kDPS)	-     🔗	✅ 19  ❌ 0  ⏭ 0    🔗	See Details
setup-environment	-     🔗	N/A	See Details

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✅  build-and-test workflow has finished in 34 minutes 42 seconds (24 minutes 25 seconds less than main branch avg.) and finished at 26th Dec, 2022.

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Job	Failed Steps	Tests
integration-tests	-     🔗	✅ 55  ❌ 0  ⏭ 0    🔗	See Details
cross-compile (darwin, amd64)	-     🔗	N/A	See Details
cross-compile (darwin, arm64)	-     🔗	N/A	See Details
cross-compile (linux, 386)	-     🔗	N/A	See Details
cross-compile (linux, arm)	-     🔗	N/A	See Details
cross-compile (linux, arm64)	-     🔗	N/A	See Details
cross-compile (linux, amd64)	-     🔗	N/A	See Details
cross-compile (linux, ppc64le)	-     🔗	N/A	See Details
cross-compile (windows, 386)	-     🔗	N/A	See Details
cross-compile (windows, amd64)	-     🔗	N/A	See Details
build-package (deb)	-     🔗	N/A	See Details
build-package (rpm)	-     🔗	N/A	See Details
windows-msi	-     🔗	N/A	See Details
publish-check	-     🔗	N/A	See Details
publish-dev	-     🔗	N/A	See Details
publish-stable	-     🔗	N/A	See Details

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[MovieStoreGuy]

Just a couple of comments but I do appreciate making the change so quickly

[MovieStoreGuy]

I am fine with these changes, however, @dmitryax and @pmcollins should verify these.

[MovieStoreGuy]

Ready to merge once @dmitryax or @pmcollins approves.

[dmitryax]

We need to add a deprecation warning log about it. Otherwise, the user will not notice the deprecation. Can be done in a follow-up PR