Reland "Text inline widgets, TextSpan rework (#30069)" with improved backwards compatibility (#34051)

This reverts commit 14414f35.

This reverts commit 86862c1e.

* Merge in changes for inline widgets

* Make analyzer happy, fix tests

* Fix analyzer

* Add missing doc

* Docs on RichText

* Fix analyzer some more

* Remove whitespace at end of line

* Update goldens

* Text fixes

* Analyzer

Add `textWidthBasis` param to Text to allow calculating width according to longest line.

This reverts commit 323108ff due to weird engine dependency bug

Add `textWidthBasis` param to Text to allow calculating width according to longest line.

Fixes https://github.com/flutter/flutter/issues/25025

This reverts commit 46cabdab.

Integrate Strut: Add StrutStyle, expose Strut API, wire up strut with dart:ui, Roll engine 31a7f4d..e7eb1c8 (7 commits) (#26332)

Includes a breaking change to dart:ui ParagraphStyle where lineHeight is renamed to height for consistency with TextStyle.

* enable lint unnecessary_new

* fix tests

* fix tests

* fix tests

This should fix https://github.com/flutter/flutter/issues/18729

I'll add a gold test, and try to figure out how to remove the saveLayer without affecting the correctness later.

This is a follow up on https://github.com/flutter/engine/pull/5420
and https://github.com/flutter/flutter/issues/18057

As you can see from the diff, we also mistakenly saveLayer before
the clip at some places previously.

I got tired of drive-by spelling fixes, so I figured I'd just take care of them all at once.

This only corrects errors in the dartdocs, not regular comments, and I skipped any sample code in the dartdocs. It doesn't touch any identifiers in the dartdocs either. No code changes, just comments.

Various improvements (in particular a new painting fuzzer) to the text manual test.

Some additional documentation.

A fix to Stack to remove an LTR bias: make unpositioned children apply "alignment".

Some more debugging information on RichText and Text.

A fix to the flutter tool to not crash when an RPC call throws an exception.

* Oct 12 10:12am

* implicit_semantics_test.dart passes

* refactoring

* works in nice

* minor rename

* more doc comments

* to be explicit check better

* fix test

* ++

* ++

* semantics_9_test (BlockSemantics) and implicit_semantics_test are passing

* doc updates

* tiny refactor

* fix static errors in tests

* fix gesture detector

* ++

* ++

* geometry

* ++

* remove noGeometry

* revert test

* +

* all tests but scrolling/clipping pass

* clipping works

* scrolling halfway

* sliver tests pass

* ALL TESTS PASS

* SemanticsNode changed

* docs and tiny fixes

* card test

* more doc comments

* remove missed print

* more tests

* make test pass on Linux

* remove changes to intellij proj file

* review comments

It has recently come to light that we may have been ordering saveLayer
calls and clip calls incorrectly.

Refactor RenderObject.toStringDeep and Widget.toStringDeep code to use DiagnosticsNode.