[iOS] Move nala symbols & color assets into core build

[kylehickinson]

This shifts the actual symbol & color asset catalog generation and compilation into the brave-core ninja build system and bundles them in a dynamic framework which will allow asset sharing between targets saving some disk space.

This change will improve incremental build times of anything that would have imported the DesignSystem target by 30s+ per build as SPM plugins were executing incorrectly every build (with no way to seemingly fix it for asset catalogs) thus causing asset catalog recompilations each time.

Resolves brave/brave-browser#42009

Submitter Checklist:

• I confirm that no security/privacy review is needed and no other type of reviews are needed, or that I have requested them
• There is a ticket for my issue
• Used Github auto-closing keywords in the PR description above
• Wrote a good PR/commit description
• Squashed any review feedback or "fixup" commits before merge, so that history is a record of what happened in the repo, not your PR
• Added appropriate labels (QA/Yes or QA/No; release-notes/include or release-notes/exclude; OS/...) to the associated issue
• Checked the PR locally:
  • npm run test -- brave_browser_tests, npm run test -- brave_unit_tests wiki
  • npm run presubmit wiki, npm run gn_check, npm run tslint
• Ran git rebase master (if needed)

Reviewer Checklist:

• A security review is not needed, or a link to one is included in the PR description
• New files have MPL-2.0 license header
• Adequate test coverage exists to prevent regressions
• Major classes, functions and non-trivial code blocks are well-commented
• Changes in component dependencies are properly reflected in gn
• Code follows the style guide
• Test plan is specified in PR before merging

After-merge Checklist:

• The associated issue milestone is set to the smallest version that the
  changes has landed on
• All relevant documentation has been updated, for instance:
  • https://github.com/brave/brave-browser/wiki/Deviations-from-Chromium-(features-we-disable-or-remove)
  • https://github.com/brave/brave-browser/wiki/Proxy-redirected-URLs
  • https://github.com/brave/brave-browser/wiki/Fingerprinting-Protections
  • https://github.com/brave/brave-browser/wiki/Brave%E2%80%99s-Use-of-Referral-Codes
  • https://github.com/brave/brave-browser/wiki/Web-Compatibility-Exceptions-in-Brave
  • https://github.com/brave/brave-browser/wiki/QA-Guide
  • https://github.com/brave/brave-browser/wiki/P3A

Test Plan:

[github-actions]

[puLL-Merge] - brave/brave-core@26416

Description

This PR introduces a new framework called "NalaAssets" to manage design assets like icons and colors for the Brave iOS app. It moves the responsibility of handling these assets from the main app target to a separate framework, which can be more easily shared and maintained.

Changes

Changes

1. ios/BUILD.gn:

   • Added a new target for creating the NalaAssets xcframework
   • Updated the "brave_ios" group to include the new NalaAssets xcframework

2. ios/brave-ios/Package.swift:

   • Added NalaAssets as a binary target
   • Updated the DesignSystem target to depend on NalaAssets

3. ios/brave-ios/Plugins/LeoAssetsPlugin/LeoAssetsPlugin.swift:

   • Removed code related to generating SF Symbols asset catalog
   • Simplified the color asset copying process

4. ios/brave-ios/Sources/BraveNews/Settings/BraveNewsAddSourceResultsViewController.swift:

   • Updated the image name from "brave.lock.alt" to "leo.lock.plain"

5. ios/brave-ios/Sources/DesignSystem/Colors/BraveColors.swift:

   • Updated color initialization to use the NalaAssets bundle

6. ios/brave-ios/Sources/DesignSystem/Icons/BraveSymbols.swift:

   • Updated image initialization to use the NalaAssets bundle

7. Removed multiple asset catalog files from the DesignSystem directory

8. Added new files for the NalaAssets framework:

   • ios/nala/BUILD.gn
   • ios/nala/Info.plist
   • ios/nala/internal/nala_bundle.m
   • ios/nala/make_symbols_asset_catalog.py
   • ios/nala/public/nala_bundle.h

9. script/ios_bootstrap.py:

   • Added NalaAssets to the list of xcframework placeholders

Possible Issues

1. The removal of multiple asset catalog files might affect existing code that directly references these assets. A thorough review of asset usage throughout the codebase is recommended.

2. The change in the image name from "brave.lock.alt" to "leo.lock.plain" in BraveNewsAddSourceResultsViewController.swift might need to be applied in other parts of the codebase as well.

3. The new build process for NalaAssets might increase build times slightly, which could affect development workflow.

Security Hotspots

There are no apparent security issues introduced by this change. The modifications primarily involve asset management and do not directly affect security-sensitive areas of the codebase.