Analyze update to use in-memory package map.

Fixes #3795

Updates the analyze command to pass a package map to analysis rather than a file path.

This allows us to avoid creating a needless temporary `.packages` file and host directory and saves us a trip to disk to retrieve the contents when building our URI resolvers for analysis.

Fix analyzer error messages.

TextAlign applies to a whole paragraph instead of applying to an individual
text span. This patch moves the property out of TextStyle and into a separate
property on Text and RichText.

Will have the result of restoring `[static warning]` to `[warning]`, etc.

(This is essentially how we handle it in the analyzer CLI.)

Fixes #3759

Analysis re-work to use analyzer APIs.

It has no more clients.

Follow-up to #3734.

Fixes #2484

* avoid sending analytics on ci systems

* review comments

* Move global analysis options file to the repo root

Also restore the analysis options file for stocks example, since
the global options trigger warnings on generated intl files.

* Remove obsolete analysis options file for Material Gallery example

Previously it used Block, which is less efficient for large numbers of items.
Also move the top margin out of the menu item to fix the baseline alignment of
the text.

Fixes #1615

Fixes #3747

Introduces a new Dart analysis wrapper that works directly with the analyzer API (in favor of shelling out to a separate process).

Some consequences:

  * we no longer need to fear parts (simplifying our dart file gathering)
  * we can filter by error code (when needed), rather than by error strings
  * no more IO scraping
  * no need to generate `main()` or to run with `--package-warnings`
  * we now specify an analyzer (and linter) version in the pubspec (we’ll want to make sure this doesn’t diverge too far from the analyzer shipped with the SDK but it does give us some room to play with experimental builds)
  * no more (re)scanning of error source files (and so no more source cache)
  * should generally be a bit simpler and easier to maintain
  * runs a bit faster :)

Fixes #3741

This patch sizes the menu such that it is always on screen, but doesn't scroll
the menu to ensure that the currently selected item is always visible and on
top of the button. That will need to wait for a later patch.

Also, teach CustomPaint how to repaint animations more efficiently.

Fixes #3720

Prefer implict `equals` matcher in test expectations.

Last literals get their types.

@Hixie: as per our conversation, a little more concise.

This test hangs occationally on the bots and the bots aren't smart enough to
recover, which means the whole project gets blocked.

Filed #3735 about the hang.

Last fixes to get the repo running clean checking for annotations on list and map literals.