Rename context to closest

[veken1199]

We are renaming context to closest in Dynamic Sources to avoid potential conflicts and build sustainably in the future.

For reference, here are examples of context usage in the theme code, and how they should appear once you rename to closest:

1. With content_for liquid tag

// Current Usage:
{% content_for "blocks", context.product: product %}

// Updated Usage:
{% content_for "blocks", closest.product: product %}

2. In json template data and presets

// Current Usage:
{{ context.product }}

// Updated Usage:
{{ closest.product }}

Follow the docs for more details:
https://shopify.dev/docs/storefronts/themes/architecture/blocks/theme-blocks/dynamic-sources