Update eslint config in packages/runtime/runtime-utils to extend "recommended" base config

[RishhiB]

The package currently uses our "minimal" config. This PR updates it to use "recommended" and fix the resulting linter violations.

AB#3022

PR Overview

This PR updates the ESLint configuration in packages/runtime/runtime-utils to extend the "recommended" base config and adjusts several files for improved type safety and consistency. Key changes include updating lint rules, standardizing UTF encoding strings from "utf-8" to "utf8", and adding explicit return types as well as minor refactoring throughout the codebase.

Reviewed Changes

File	Description
packages/runtime/runtime-utils/.eslintrc.cjs	Changed ESLint config from a deprecated minimal config to the recommended configuration.
packages/runtime/runtime-utils/src/dataStoreHelpers.ts	Updated type definitions and error handling logic for improved type safety.
packages/runtime/runtime-utils/src/handles.ts	Refactored type checking for serialized handles using unknown type.
packages/runtime/runtime-utils/src/unpackUsedRoutes.ts	Minor refactoring of conditional logic in accumulating child routes.
packages/common/driver-definitions/src/protocol/storage.ts	Standardized encoding strings from "utf-8" to "utf8".
packages/runtime/runtime-utils/src/summaryUtils.ts	Added new functions with explicit return types and updated UTF‑8 byte length calculation logic.
packages/runtime/runtime-utils/src/requestParser.ts	Refactored URL path extraction and added explicit return types.
packages/runtime/runtime-utils/src/runtimeFactoryHelper.ts	Improved type annotations for factory helper class.
packages/runtime/runtime-utils/src/objectstorageutils.ts	Updated string slicing and adjusted condition for path existence checking.
packages/loader/driver-utils/src/blob.ts	Standardized encoding strings in blob constructor.
packages/loader/driver-utils/src/treeConversions.ts	Standardized encoding strings and minor adjustments in tree conversion.
Various test files	Updated import paths and added explicit typing for better clarity and Node.js compatibility.
packages/runtime/runtime-utils/src/utils.ts	Added explicit return type and replaced fromCharCode with fromCodePoint for compact ID encoding.

Copilot reviewed 17 out of 17 changed files in this pull request and generated no comments.

Comments suppressed due to low confidence (1)

packages/runtime/runtime-utils/src/summaryUtils.ts:71

• Verify that the iteration and index decrement logic correctly handles multi-code-unit characters after switching from charCodeAt to codePointAt to ensure the accurate calculation of UTF-8 byte length.

const code = str.codePointAt(i);

[github-actions]

🔗 Found some broken links! 💔

Run a link check locally to find them. See
https://github.com/microsoft/FluidFramework/wiki/Checking-for-broken-links-in-the-documentation for more information.

linkcheck output

> fluid-framework-docs-site@0.0.0 ci:check-links /home/runner/work/FluidFramework/FluidFramework/docs
> start-server-and-test "npm run serve -- --no-open" 3000 check-links

1: starting server using command "npm run serve -- --no-open"
and when url "[ 'http://127.0.0.1:3000' ]" is responding with HTTP status code 200
running tests using command "npm run check-links"


> fluid-framework-docs-site@0.0.0 serve
> docusaurus serve --no-open

[SUCCESS] Serving "build" directory at: http://localhost:3000/

> fluid-framework-docs-site@0.0.0 check-links
> linkcheck http://localhost:3000 --skip-file skipped-urls.txt

Crawling...

http://localhost:3000/docs/data-structures/tree
- (36:97) 'the Shar..' => http://localhost:3000/docs/api/tree (HTTP 404)

http://localhost:3000/docs/data-structures/tree/
- (36:97) 'the Shar..' => http://localhost:3000/docs/api/tree (HTTP 404)

http://localhost:3000/docs/data-structures/tree/schema-definition
- (30:128) 'SharedTr..' => http://localhost:3000/docs/api/tree (HTTP 404)

http://localhost:3000/docs/start/tree-start
- (44:4) 'the API ..' => http://localhost:3000/docs/api/tree/schemafactory-class (HTTP 404)
- (61:7) 'the API' => http://localhost:3000/docs/api/tree/treechangeevents-interface (HTTP 404)


Stats:
  158264 links
    1304 destination URLs
    1535 URLs ignored
       0 warnings
       3 errors

 ELIFECYCLE  Command failed with exit code 1.