[pkg/ottl] Update functions to use StringGetter

[TylerHelmuth]

Description:
Updates functions that expect a string to use StringGetter. This simplifies the functions and works towards a standard function error pattern where the functions errors if it does not have the data it needs. Erroring is safe thanks to error mode.

Link to tracking Issue:

Relates to #16519

Testing:
Updated tests

Documentation:
Updated docs

[runforesight]

Foresight Summary

    
Major Impacts

build-and-test-windows duration(6 seconds) has decreased 36 minutes 32 seconds compared to main branch avg(36 minutes 38 seconds).

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⭕  build-and-test-windows workflow has finished in 6 seconds (36 minutes 43 seconds less than main branch avg.) and finished at 21st Mar, 2023.

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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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✅  telemetrygen workflow has finished in 54 seconds (47 seconds less than main branch avg.) and finished at 21st Mar, 2023.

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✅  check-links workflow has finished in 1 minute 34 seconds and finished at 21st Mar, 2023.

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✅  changelog workflow has finished in 1 minute 52 seconds and finished at 21st Mar, 2023.

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✅  build-and-test workflow has finished in 35 minutes 55 seconds (16 minutes 45 seconds less than main branch avg.) and finished at 21st Mar, 2023.

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Job	Failed Steps	Tests
unittest-matrix (1.20, connector)	-     🔗	✅ 126  ❌ 0  ⏭ 0    🔗	See Details
unittest-matrix (1.19, connector)	-     🔗	✅ 126  ❌ 0  ⏭ 0    🔗	See Details
correctness-metrics	-     🔗	✅ 2  ❌ 0  ⏭ 0    🔗	See Details
unittest-matrix (1.20, internal)	-     🔗	✅ 583  ❌ 0  ⏭ 0    🔗	See Details
unittest-matrix (1.19, internal)	-     🔗	✅ 583  ❌ 0  ⏭ 0    🔗	See Details
correctness-traces	-     🔗	✅ 17  ❌ 0  ⏭ 0    🔗	See Details
unittest-matrix (1.20, processor)	-     🔗	✅ 1557  ❌ 0  ⏭ 0    🔗	See Details
unittest-matrix (1.20, extension)	-     🔗	✅ 543  ❌ 0  ⏭ 0    🔗	See Details
unittest-matrix (1.19, processor)	-     🔗	✅ 1557  ❌ 0  ⏭ 0    🔗	See Details
unittest-matrix (1.19, extension)	-     🔗	✅ 543  ❌ 0  ⏭ 0    🔗	See Details
unittest-matrix (1.19, receiver-0)	-     🔗	✅ 2611  ❌ 0  ⏭ 0    🔗	See Details
unittest-matrix (1.20, receiver-0)	-     🔗	✅ 2611  ❌ 0  ⏭ 0    🔗	See Details
unittest-matrix (1.19, exporter)	-     🔗	✅ 2501  ❌ 0  ⏭ 0    🔗	See Details
unittest-matrix (1.20, other)	-     🔗	✅ 4746  ❌ 0  ⏭ 0    🔗	See Details
unittest-matrix (1.19, other)	-     🔗	✅ 4746  ❌ 0  ⏭ 0    🔗	See Details
integration-tests	-     🔗	✅ 55  ❌ 0  ⏭ 0    🔗	See Details
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build-examples	-     🔗	N/A	See Details
unittest-matrix (1.20, receiver-1)	-     🔗	N/A	See Details
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✅  prometheus-compliance-tests workflow has finished in 3 minutes 27 seconds (3 minutes 24 seconds less than main branch avg.) and finished at 21st Mar, 2023.

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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 6 minutes 54 seconds (5 minutes 6 seconds less than main branch avg.) and finished at 21st Mar, 2023.

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Job	Failed Steps	Tests
loadtest (TestTraceAttributesProcessor)	-     🔗	✅ 3  ❌ 0  ⏭ 0    🔗	See Details
loadtest (TestIdleMode)	-     🔗	✅ 1  ❌ 0  ⏭ 0    🔗	See Details
loadtest (TestMetric10kDPS|TestMetricsFromFile)	-     🔗	✅ 6  ❌ 0  ⏭ 0    🔗	See Details
loadtest (TestTraceNoBackend10kSPS|TestTrace1kSPSWithAttrs)	-     🔗	✅ 8  ❌ 0  ⏭ 0    🔗	See Details
loadtest (TestTraceBallast1kSPSWithAttrs|TestTraceBallast1kSPSAddAttrs)	-     🔗	✅ 10  ❌ 0  ⏭ 0    🔗	See Details
loadtest (TestMetricResourceProcessor|TestTrace10kSPS)	-     🔗	✅ 12  ❌ 0  ⏭ 0    🔗	See Details
loadtest (TestBallastMemory|TestLog10kDPS)	-     🔗	✅ 18  ❌ 0  ⏭ 0    🔗	See Details
setup-environment	-     🔗	N/A	See Details

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✅  e2e-tests workflow has finished in 12 minutes 31 seconds (2 minutes 36 seconds less than main branch avg.) and finished at 21st Mar, 2023.

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Job	Failed Steps	Tests
kubernetes-test (v1.26.0)	-     🔗	N/A	See Details
kubernetes-test (v1.25.3)	-     🔗	N/A	See Details
kubernetes-test (v1.24.7)	-     🔗	N/A	See Details
kubernetes-test (v1.23.13)	-     🔗	N/A	See Details

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[TylerHelmuth]

Gotta submit error_mode options for filterprocessor and routingprocessor first.

[TylerHelmuth]

Now depends on #19629

[MovieStoreGuy]

I'm excited to see more usage of this :D

[evan-bradley]

This could be done in a follow-up, but I think it would also make sense to transition ReplaceMatch and ReplacePattern to use StringGetters as well.