refactor: unify how executor tests are written (#2042)

* feat: use TaskTest for executor tests

* feat: more tests

* feat: separate tests for executing and formatting with new functional options that work for both test types

* feat: formatter tests

* refactor: more tests

testdata/alias/testdata/TestAlias-alias.golden

@@ -0,0 +1,6 @@
+task: [foo] echo "foo"
+foo
+task: [bar] echo "bar"
+bar
+task: [included:qux] echo "qux"
+qux

testdata/alias/testdata/TestAlias-alias_summary.golden

@@ -0,0 +1,11 @@
+task: foo
+
+(task does not have description or summary)
+
+aliases:
+ - f
+ - x
+
+commands:
+ - echo "foo"
+ - Task: b

testdata/alias/testdata/TestAlias-duplicate_alias-err-run.golden

@@ -0,0 +1 @@
+task: Found multiple tasks (foo, bar) that match "x"