RUM-6245 Improve image hashing memory footprint

[maxep]

What and why?

Compute the image hash on a greyscale colour space image scaled down to 100 pixels in width or height.

Context in RFC (internal)

How?

Use Core Graphics to draw the image in a greyscale colour space.

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
• [ ] Add CHANGELOG entry for user facing changes

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

Datadog Report

Branch report: maxep/RUM-6245/sr-image-processing Commit report: 9e356d4 Test service: dd-sdk-ios

:white_check_mark: 0 Failed, 3470 Passed, 0 Skipped, 2m 21.59s Total Time :snowflake: 1 New Flaky :small_red_triangle_down: Test Sessions change in coverage: 3 decreased, 4 increased, 7 no change

New Flaky Tests (1)

• testWhenEnabled_itSendsConfigurationTelemetry - SessionReplayTests - Last Failure

  Expand for error

  ``` Assertion Failure at SessionReplayTests.swift:198: XCTUnwrap failed: expected non-nil value of type "ConfigurationTelemetry" ```

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

• test DatadogTraceTests iOS 54.17% (-0.1%) - Details
• test DatadogCoreTests iOS 72.67% (-0.02%) - Details
• test DatadogInternalTests tvOS 79.5% (-0.02%) - Details