test(widgets): add JVM unit and composable tests for ScaleBar

[dkhawk]

Description

Stacked PR on top of #1001 (feature/robolectric-tests).

Introduces JVM unit and Compose integration tests using Robolectric and the local shadow library for maps-compose-widgets, bringing module line coverage up from 0.00% to 67.12% (instruction coverage from 0.00% to 80.68%).

Summary of Changes

• Added test dependencies (robolectric, mockk, truth, androidx.test.compose.ui, maps.robolectric.shadows) in maps-compose-widgets/build.gradle.kts.
• Configured Robolectric Android resources and Java 21 test runner toolchain.
• Added debug manifest with ComponentActivity for Robolectric Compose rule hosting.
• Added ScaleBarTest.kt covering canvas distance calculation, unit conversions (ft, mi), ScaleBar composable rendering, and DisappearingScaleBar camera position animation/state changes.

cc @LoyalAbbas @kikoso

[github-actions]

Coverage (unit tests)

No unit baseline recorded in coverage/history.csv yet, so this run only reports absolute numbers.

Module	Line %	Change	Branch %	Change
maps-compose	36.56%	new	10.32%	new
maps-compose-utils	2.04%	new	0.49%	new
maps-compose-widgets	67.12%	new	52.94%	new
TOTAL	31.19%	new	9.82%	new

_{Line and branch coverage from unit test reports. History is recorded in coverage/history.csv after each merge to feature/robolectric-tests.}

[googlemaps-bot]

Code Coverage

Overall Project	24.67%	❌

There is no coverage information present for the Files changed