* In `_handleServerResponse`, use if-case with map patterns to avoid
casts and null checks and repeatedly fetching map values.
* Remove the castStringKeyedMap utility. After some other changes,
most call-sites passed in a Map, so then half of the utility is not
used. In the others, it seemed simplest to use `as Map` and `.cast()`
inline.
* Change some `dynamic` local variables to be `Object?` instead.
* Replace `DartdevCommand.project` getter and `_project` field with a
single final field.
* Remove unused properties from `Project` and unused `PackageConfig`
class.
* Remove associated tests.
Change-Id: I1f626ecc0e6e4d27ef24f65959fd4cb54fb5fc92
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/412980
Reviewed-by: Devon Carew <devoncarew@google.com>
Commit-Queue: Samuel Rawlins <srawlins@google.com>
Sam Rawlins
539840f91c