Support per-blob queries in snippets

What does this MR do?

As per the relevant issue this MR introduces:

1. [BE] Updated GraphQL schema for snippet and blobs within it
2. [FE] Disabled batching for GraphQL queries within the snippet Vue application
3. [FE] Per-blob query (employing updated data structure introduced in 1.) to get the blob's content

Screenshots

Note:

• discrete rendering of the blobs: all blobs' contents are fetched independently from each other in this MR
• discrete network requests to get graphql data (this MR) instead of a massive one (current master), containing all contents
• significant decrease (1.7 MB vs. 73.4 MB) of data transferred in the network requests due to not fetching content for the too large blobs that are not rendered anyway

	Before	After
Rendering
Network request

Since multi-file snippets are still behind the feature flag (:snippet_multiple_files), there's no changelog entry provided

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry feature flag
• [-] Documentation (if required) feature flag
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

References #254198 (closed)