[internal/core] migrate semconv from v1.18.0

[codeboten]

Component(s)

internal/core

Describe the issue you're reporting

While removing usage of old semconv imports, i found that this package uses semantic conventions that rely on v1.18.0. Specifically the following attributes:

faas.execution
http.user_agent

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[github-actions]

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[github-actions]

Pinging code owners:

• internal/core: @open-telemetry/collector-approvers

See Adding Labels via Comments if you do not have permissions to add labels yourself.