Fix forceFlush issue for Lambda Instrumentation and optimizations

[mxiamxia]

Description of changes:

1. Replicate Python SDK changes Changing span unsampled flag to be sampled flag aws-otel-python-instrumentation#260 to rename Unsampled span attribute flag name.
2. Optimize Lambda Layer Deps package config to reduce layer size.
3. Fixed the forceFlush issue which is to set TraceProvider for all instrumentations at the end of init configuration

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