[refactor] Update SvelteLDClient to use proxy for flag variations. Allows to track flag evaluations

[nosnibor89]

This pull request includes several significant changes to the SvelteLDClient in the svelte SDK package. The changes focus on improving the handling of flag variations, updating dependencies, and adding a new proxy mechanism for flag access.

Improvements to flag variation handling:

• packages/sdk/svelte/src/lib/client/SvelteLDClient.ts: Added a new toFlagsProxy function to create a proxy for the flags object, which intercepts access to flag values and returns the appropriate variation. This ensures that the flag values are correctly fetched from the LaunchDarkly client.

Updates to dependencies:

• packages/sdk/svelte/package.json: Removed @launchdarkly/js-client-sdk-common from both peerDependencies and dependencies.

Enhancements to test cases:

• packages/sdk/svelte/__tests__/lib/client/SvelteLDClient.test.ts: Modified the variation mock to return the default value and added an event emission for the 'ready' event to set initial flag values in the test cases. [1] [2]

Refactoring for consistency:

• packages/sdk/svelte/src/lib/client/SvelteLDClient.ts: Replaced references to jsSdk with coreLdClient for consistency and clarity in the createLD function. [1] [2] [3]