Disable location sharing when no MapTiler config is available

LocationService now exposes the MapTiler config to use: the one provided by the
homeserver takes precedence over the build time one, and null means that no map
provider is configured. It is now session scoped, and isServiceAvailable()
returns a StateFlow derived from this config.

When no config is available:
- the location sharing option is hidden from the composer, and location events
  cannot be opened in the location viewer;
- the "Location sharing" entry is hidden from the settings;
- location events in the timeline render a placeholder, without performing any
  request to MapTiler.

The show and share location screens now get the config from LocationService
rather than fetching the homeserver config by themselves.

Closes element-hq/element-android-enterprise#69

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

features/location/test/build.gradle.kts

@@ -16,6 +16,7 @@ android {
 
 dependencies {
     api(projects.features.location.api)
+    implementation(projects.features.enterprise.api)
     implementation(projects.libraries.architecture)
     implementation(projects.libraries.matrix.api)
     implementation(projects.tests.testutils)