This reverts commit 275ab9c6.

Revert "Reland "Remove references to Observatory (#118577)""

Revert "[flutter_tools] show web-server in flutter devices"

This reverts commit 298d8c76.

[flutter_tools] show web-server in flutter devices

This reverts commit 2df140f4.

Observatory is being deprecated for Dart 3.0 so it should no longer be
referenced in tooling messaging / flags.

See https://github.com/dart-lang/sdk/issues/50233

* [web] Put all index.html operations in one place

* review comments

* fix build

* change quotes

* fix test

* Remove superfluous words.

* Update packages/flutter/lib/src/widgets/slotted_render_object_widget.dart
Co-authored-by: Michael Goderbauer <goderbauer@google.com>

Update test expectations from application/javascript -> text/javascript

`package:mime` now uses `text/javascript` and not `application/javascript`.

See https://github.com/dart-lang/mime/pull/76.
See https://datatracker.ietf.org/doc/html/rfc9239.

> This document defines equivalent processing requirements for the various script media types. The most widely supported media type in use is `text/javascript`; all others are considered historical and obsolete aliases of `text/javascript`.

* [tools]some ui polish for build ipa validation

* do not print out a few success validations

* rename installed type to success for more general usage

* forgot nit after reverting custom validation types and re-use doctor types

* update flutter build command

* update tests

* fix analyze suggestions

This reverts commit 53e68762.

* allow marking a golden check as flaky

* add matchesFlutterGolden to analyze.dart; no tags for flutter_goldens/lib

* Pause

* ++

* ++

* Analyzer therapy

* Once more with feeling

* Nits

* Review feedback

* Silly oops

* Test progress

* More tests

* Finish

* Nits

* Analyzer

* Review feedback
Co-authored-by: Yegor Jbanov <yjbanov@google.com>

* Migrate packages/flutter_tools/test/general.shard, part 2/2

* Fix analysis

* Fix tests

* Fix analysis

* Apply suggestions from code review
Co-authored-by: Christopher Fujino <fujino@google.com>
Co-authored-by: Christopher Fujino <fujino@google.com>

Revert "Read dart_plugin_registrant path from FlutterProject to support non-standard path." (#107850)

* Provide flutter sdk kernel files to dwds launcher instead of dart ones

* Update log test to report all warnings

* Update licences for new files

* Addressed CR comments

* Addressed CR comments

This reverts commit 5fd259be.