opentelemetry-instrumentation-aws-lambda: Fix aws lambda span creation

[herin049]

Description

Fixes bug where the Lambda invocation Span name would be incorrectly set to the name of the Python handler function instead of the function name. Also fixes an issue where the Lambda invocation Span kind would occasionally not be set to SERVER which violates the OpenTelemetry FaaS semantic conventions.

Fixes #3963

Type of change

Please delete options that are not relevant.

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] This change requires a documentation update

How Has This Been Tested?

Unit tests have been updated to reflect changing the invocation Span name to the Lambda function name and changing the Span kind to always be SERVER.

Does This PR Require a Core Repo Change?

• [ ] Yes. - Link to PR:
• [x] No.

Checklist:

See contributing.md for styleguide, changelog guidelines, and more.

• [x] Followed the style guidelines of this project
• [x] Changelogs have been updated
• [x] Unit tests have been added