This PR modifies the web build slightly to create an `AssetManifest.json`, that is a JSON(base64)-encoded version of the `AssetManifest.bin` file.

_(This should enable all browsers to download the file without any interference, and all servers to serve it with the correct headers.)_

It also modifies Flutter's `AssetManifest` class so it loads and uses said file `if (kIsWeb)`.

### Issues

* Fixes https://github.com/flutter/flutter/issues/124883

### Tests

* Unit tests added.
* Some tests that run on the Web needed to be informed of the new filename, but their behavior didn't have to change (binary contents are the same across all platforms).
* I've deployed a test app, so users affected by the BIN issue may take a look at the PR in action:
  * https://dit-tests.web.app

rename generated asset manifest file back to `AssetManifest.bin` (from `AssetManifest.smcbin`) (#128529)

Closes https://github.com/flutter/flutter/issues/128456, which is now linked to in a code comment in this change.
Reopens https://github.com/flutter/flutter/issues/124883.

This effectively reverts https://github.com/flutter/flutter/pull/126077 and is intended to be cherry-picked into stable.

Fixes #124883. Will require a g3fix.

Renames `AssetManifest.bin` to `AssetManifest.smcbin` (madeup extension for "Standard Message Codec binary").

* stop recursively including assets from asset directories

* remove unused imports

* lint

This reverts commit da36bd6f.

* add test

* fix

* use preexisting testFileSystem

* fix variant tests

* Revert "use preexisting testFileSystem"

This reverts commit b6df288ef4a6ff007ecd984e98a1a3f2001ad242.

* nit: grammar

* [flutter_tools] re-enable web shader compilation

* update test cases

* initial

* update asset_bundle_package_test

* Update asset_bundle_test.dart

* Update asset_bundle_package_fonts_test.dart

* update pubspec checksum for smc dependency

* flutter update-packages --force-upgrade

* prefer += 1 over ++
Co-authored-by: Jonah Williams <jonahwilliams@google.com>

* add regexp comment

* rescope int list comparison function

* update packages
Co-authored-by: Jonah Williams <jonahwilliams@google.com>

Revert "Speed up first asset load by encoding asset manifest in binary rather than JSON (#113637)" (#116662)

This reverts commit 56cad89b.

* [flutter_tools] use absolute path for shader lib

* update tests

This reverts commit 5fd259be.

* opt out the flutter tool

* oops EOF

* fix import

* Update tool_backend.dart

* Update daemon_client.dart

* fix more

[flutter_tools] remove most globals from asset system and remove Cache manipulation in unit tests (#70011)

Fixes #45075
Fixes #57210

If an asset was included directly from the project root directory, then the same asset when copied to various output or ephemeral directories would also be picked up as an asset variant. This could cause assets to be recursively copied into asset/build/ephemeral directories, as each time it would run it would pick up all of the previous "variants".

The solution is to include project ephemeral directories, in addition to the build directory.

The global packages path could cause tests to fail when it would be overriden to unexpected (in test setup) values. Remove most usage and make it a configuration on buildInfo, along with most other build information. Cleanup the asset builder to require the .packages path and the resident runners to no longer require it, since they already have the information in build_info.

It needs to stick around for the fuchsia deps we do not control.

Filled #60232 for remaining work.

If a dependency specified uses-material-design: true and the main pubspec specifies uses-material-design: false, then the MaterialIcons font would be included in the font manifest, but not in the AssetManifest or final bundle. Remove it from the FontManifest if this occurs