feat: upgrade lambda runtime from 18x to 20x #4772

Job	Run time
Verify examples (1.5.6, default)	34s
Verify examples (1.5.6, ubuntu)	16s
Verify examples (1.5.6, prebuilt)	10s
Verify examples (1.5.6, arm64)	22s
Verify examples (1.5.6, ephemeral)	16s
Verify module (1.5.6)	21s
Verify examples (1.5.6, windows)	14s
Verify module (latest)	29s
Verify examples (1.5.6, multi-runner)	24s
Verify examples (latest, default)	15s
Verify examples (latest, ubuntu)	16s
Verify examples (latest, prebuilt)	11s
Verify examples (latest, arm64)	15s
Verify examples (latest, ephemeral)	20s
Verify modules (1.3.2, ami-housekeeper)	40s
Verify examples (latest, windows)	9s
Verify modules (1.3.2, download-lambda)	17s
Verify examples (latest, multi-runner)	22s
Verify modules (1.3.2, multi-runner)	38s
Verify modules (1.3.2, runner-binaries-syncer)	29s
Verify modules (1.3.2, runners)	41s
Verify modules (1.3.2, setup-iam-permissions)	15s
Verify modules (1.3.2, ssm)	37s
Verify modules (1.3.2, webhook)	22s
Verify modules (latest, ami-housekeeper)	13s
Verify modules (latest, download-lambda)	15s
Verify modules (latest, multi-runner)	23s
Verify modules (latest, runner-binaries-syncer)	25s
Verify modules (latest, runners)	24s
Verify modules (latest, setup-iam-permissions)	24s
Verify modules (latest, ssm)	25s
Verify modules (latest, webhook)	17s
	11m 39s

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