feat(agent): Add nonce to RUM scripts

[poespas]

We ran into the problem that our users can't have a CSP-secure website because of the injected inline RUM scripts without a nonce-attribute, this PR will be able to add the nonce when it's set through the php ini configuration:

Example:

newrelic.browser_monitoring.nonce_rum_header="abc123"
newrelic.browser_monitoring.nonce_rum_footer="abc456"

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1 out of 2 committers have signed the CLA.

✅ poespas
❌ Jonathan Visser

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