feat: Add language-specific Renovate presets for all SDK languages

[jsonbailey]

Summary

Adds Renovate preset files for all remaining SDK languages. Each preset extends the base sdk preset (monthly schedule, 7-day minimum release age, gh-actions pinning) and disables the language's package datasource so only GitHub Actions refs are managed.

File	Datasource disabled	Repos
sdk-dotnet.json	nuget	dotnet-core, dotnet-eventsource, dotnet-cache, dotnet-logging + adapters, openfeature-dotnet, restwrappers, xamarin
sdk-go.json	go	go-server-sdk, go-server-sdk-dynamodb, go-server-sdk-redis-*
sdk-java.json	maven	java-core, okhttp-eventsource, openfeature-java-server, java-server-sdk-dynamodb, java-logging, android-client-sdk
sdk-rust.json	crate	rust-server-sdk, rust-eventsource-client, rust-sdk-events
sdk-php.json	packagist	php-server-sdk, php-server-sdk-redis-*, openfeature-php-server, php-server-sdk-otel
sdk-swift.json	pod	ios-client-sdk, swift-eventsource, swift-launchdarkly-observability
sdk-haskell.json	hackage	haskell-server-sdk, haskell-server-sdk-redis-hedis

Single-repo languages (flutter, erlang, lua, apex, c++, roku) use the base sdk preset directly — no language-specific preset needed.