RUMM-895 Add single API to configure all endpoints

[ncreated]

What and why?

📦 This PR introduces new APIs to configure Logs / Traces / RUM endpoint:

.set(endpoint: DatadogEndpoint) // .us | .eu | .gov
.set(customLogsEndpoint: URL)
.set(customTracesEndpoint: URL)
.set(customRUMEndpoint: URL)

It also marks old APIs as deprecated:

.set(logsEndpoint:)   // .us | .eu | .gov | .custom(...)
.set(tracesEndpoint:) // .us | .eu | .gov | .custom(...)
.set(rumEndpoint:)    // .us | .eu | .gov | .custom(...)

Old APIs were inconsistent: it made no sense to configure one feature for .us and another for .eu, because clientToken / RUM application ID are valid in only one server instance. Because default value was .us, this was leading to misconfigurations for clients who only set it to .eu for one product.

How?

Because we still need to support old APIs (while they are deprecated), following rules were implemented and tested:

• if DatadogEndpoint is set, it overwrites values set for LogsEndpoint, TracesEndpoint and RUMEndpoint,
• if custom<feature>Endpoint is set, it overwrites the value for that feature endpoint (including the value coming from DatadogEndpoint).

I also updated configuration tests in the way that makes it easier to remove old logic in the future.

Review checklist

• Feature or bugfix MUST have appropriate tests (unit, integration)
• Make sure each commit and the PR mention the Issue number or JIRA reference

[mariusc83]

LGTM