RUM-6386 Add default value to replaySampleRate

[mariedm]

What and why?

We decided to add a default value for session replay sample rate. This aligns with other public APIs which all provide a default value for sampling rates.

How?

• Added a default value of 100 to replaySampleRate for both Session Replay Configuration public APIs
• Updates tests accordingly

Review checklist

• [x] Feature or bugfix MUST have appropriate tests (unit, integration)
• [x] Make sure each commit and the PR mention the Issue number or JIRA reference
• [ ] Add CHANGELOG entry for user facing changes

[datadog-datadog-prod-us1[bot]]

Datadog Report

Branch report: RUM-6386-config-default-sr-sample-rate Commit report: 1734c25 Test service: dd-sdk-ios

:white_check_mark: 0 Failed, 3486 Passed, 0 Skipped, 2m 37.75s Total Time :small_red_triangle_down: Test Sessions change in coverage: 3 decreased, 5 increased, 6 no change

:small_red_triangle_down: Code Coverage Decreases vs Default Branch (3)

• test DatadogCoreTests tvOS 78.52% (-0.19%) - Details
• test DatadogTraceTests iOS 54.14% (-0.13%) - Details
• test DatadogInternalTests iOS 79.47% (-0.02%) - Details

[mariedm]

Thanks for the review @maciejburda! I'll wait next week to discuss this with the team and @jonathanmos before merging.