feat: built-in test runner and new `test` command (#1874)

feat: built-in test runner and new `test` command (#1874)

* first draft of alire test runner

* use fixed output file name in test runner

* add exe suffix when spawning tests (windows compat)

* move test runner to libalire

* add "dim_output" option to non-capturing spawns

* manifest [test] section support

* generate test crate skeleton in `alr init`

* move old test command to `index-test`

* new `test` command

* test filtering, formatting

* use index-test in testsuite

* change references to 'alr test' to 'alr index-test' in documentation and comments

* fix crash on first test run

* tests for revamped test command

* fix broken tests

* remove test-runner command

* address comments

* change default test crate name to `<mycrate>_tests`

* fix broken test

* make example test pass by default

* add support for legacy actions behaviour and multiple test runners

* fix misused build boolean success

* address review comments

* Fix dependencies

* better manifest parsing for test section

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Co-authored-by: Alejandro R. Mosteo <amosteo@unizar.es>