Add a GetExpand trait for initializing Expand objects in our tasks (#3553)

* Release 8.7.1 (hotfix) (#3459)

* Remove the retention policy setting (#3452)

---------

Co-authored-by: Cheick Keita <chkeita@microsoft.com>

* Revert "Release 8.7.1 (hotfix) (#3459)" (#3468)

This reverts commit c69deed.

* Add a ToExpand trait

* Implement ToExpand for CommonConfig

* Rename to GetExpand and implement for all task configs

* Add proptest to the crate and a simple test function (broken)

* Fix import issues

* Add config tests for analysis task

* Implement tests for merge task

* Return Result from get_expand() and implement for the rest of the configs

* Resolve merge conflict

* Undo comment

* Update comments

* Undo unintentional changes

* Add missing newline

* Fix build checks

* Fix build checks - lifetime elision

* Fix linux test imports

* Fix indented line

* Fix build checks

* Replace common test code with a declarative macro

* Format code

* Simplify URL arbitrary even further to guarantee that it's parseable

* Upgrade proptest version

* Implement Default for CommonConfig

* Remove the GetExpand trait

* Return Expand instead of Result<Expand>

* cargo fmt

* Remove unused import

* Fix PR comments (see full message for details)

- Stop initializing target_exe in get_expand() for the dotnet coverage task
  since it's overwritten when the expander is used.
 - Expand the inputs field from the generic merge task as generated_inputs.

* Update dotnet coverage task Expander tests

* Remove incorrect expansion variable from generic merge task

---------

Co-authored-by: Adam <103067949+AdamL-Microsoft@users.noreply.github.com>
Co-authored-by: Cheick Keita <chkeita@microsoft.com>

Author: 3 people

CURRENT_VERSION

@@ -1 +1 @@
-8.9.0
+8.9.0

src/agent/Cargo.lock

@@ -85,4 +85,6 @@ schemars = { version = "0.8.12", features = ["uuid1"] }
 
 [dev-dependencies]
 pretty_assertions = "1.4"
+proptest = "1.3.1"
 tempfile = "3.8"
+dunce = "1.0"