Introduce notion of a test group, use for CA tests

Grouping our tests should make it easier to understand the intent than
one long poorly-arranged list. It also is convenient for running just
the tests for a specific component when working on that component.

We need at least one test group so this isn't dead code; I decided to
collect the tests for the `ca-derivations` and `dynamic-derivations`
experimental features in groups. Do
```bash
make ca.test-group -jN
```
and
```bash
make dyn-drv.test-group -jN
```
to try running just them.

I originally did this as part of #8397 for being able to just the local
overlay store alone. I am PRing it separately now so we can separate
general infra from new features.

tests/ca/local.mk

@@ -0,0 +1,27 @@
+ca-tests := \
+  $(d)/build-with-garbage-path.sh \
+  $(d)/build.sh \
+  $(d)/concurrent-builds.sh \
+  $(d)/derivation-json.sh \
+  $(d)/duplicate-realisation-in-closure.sh \
+  $(d)/gc.sh \
+  $(d)/import-derivation.sh \
+  $(d)/new-build-cmd.sh \
+  $(d)/nix-copy.sh \
+  $(d)/nix-run.sh \
+  $(d)/nix-shell.sh \
+  $(d)/post-hook.sh \
+  $(d)/recursive.sh \
+  $(d)/repl.sh \
+  $(d)/selfref-gc.sh \
+  $(d)/signatures.sh \
+  $(d)/substitute.sh \
+  $(d)/why-depends.sh
+
+install-tests-groups += ca
+
+clean-files += \
+  $(d)/config.nix
+
+test-deps += \
+  tests/ca/config.nix

tests/dyn-drv/local.mk

@@ -0,0 +1,11 @@
+dyn-drv-tests := \
+  $(d)/text-hashed-output.sh \
+  $(d)/recursive-mod-json.sh
+
+install-tests-groups += dyn-drv
+
+clean-files += \
+  $(d)/config.nix
+
+test-deps += \
+  tests/dyn-drv/config.nix

tests/local.mk

@@ -14,7 +14,6 @@ nix_tests = \
   flakes/absolute-paths.sh \
   flakes/build-paths.sh \
   flakes/flake-in-submodule.sh \
-  ca/gc.sh \
   gc.sh \
   nix-collect-garbage-d.sh \
   remote-store.sh \
@@ -27,8 +26,6 @@ nix_tests = \
   user-envs-migration.sh \
   binary-cache.sh \
   multiple-outputs.sh \
-  ca/build.sh \
-  ca/new-build-cmd.sh \
   nix-build.sh \
   gc-concurrent.sh \
   repair.sh \
@@ -46,24 +43,17 @@ nix_tests = \
   referrers.sh \
   optimise-store.sh \
   substitute-with-invalid-ca.sh \
-  ca/concurrent-builds.sh \
   signing.sh \
-  ca/build-with-garbage-path.sh \
   hash.sh \
   gc-non-blocking.sh \
   check.sh \
-  ca/substitute.sh \
   nix-shell.sh \
-  ca/signatures.sh \
-  ca/nix-shell.sh \
-  ca/nix-copy.sh \
   check-refs.sh \
   build-remote-input-addressed.sh \
   secure-drv-outputs.sh \
   restricted.sh \
   fetchGitSubmodules.sh \
   flakes/search-root.sh \
-  ca/duplicate-realisation-in-closure.sh \
   readfile-context.sh \
   nix-channel.sh \
   recursive.sh \
@@ -79,10 +69,7 @@ nix_tests = \
   nar-access.sh \
   pure-eval.sh \
   eval.sh \
-  ca/post-hook.sh \
   repl.sh \
-  ca/repl.sh \
-  ca/recursive.sh \
   binary-cache-build-remote.sh \
   search.sh \
   logging.sh \
@@ -107,13 +94,8 @@ nix_tests = \
   fmt.sh \
   eval-store.sh \
   why-depends.sh \
-  ca/why-depends.sh \
   derivation-json.sh \
-  ca/derivation-json.sh \
   import-derivation.sh \
-  ca/import-derivation.sh \
-  dyn-drv/text-hashed-output.sh \
-  dyn-drv/recursive-mod-json.sh \
   nix_path.sh \
   case-hack.sh \
   placeholders.sh \
@@ -122,8 +104,7 @@ nix_tests = \
   build.sh \
   build-delete.sh \
   output-normalization.sh \
-  ca/nix-run.sh \
-  selfref-gc.sh ca/selfref-gc.sh \
+  selfref-gc.sh \
   db-migration.sh \
   bash-profile.sh \
   pass-as-file.sh \
@@ -147,16 +128,12 @@ install-tests += $(foreach x, $(nix_tests), $(d)/$(x))
 
 clean-files += \
   $(d)/common/vars-and-functions.sh \
-  $(d)/config.nix \
-  $(d)/ca/config.nix \
-  $(d)/dyn-drv/config.nix
+  $(d)/config.nix
 
 test-deps += \
   tests/common/vars-and-functions.sh \
   tests/config.nix \
-  tests/ca/config.nix \
-  tests/test-libstoreconsumer/test-libstoreconsumer \
-  tests/dyn-drv/config.nix
+  tests/test-libstoreconsumer/test-libstoreconsumer
 
 ifeq ($(BUILD_SHARED_LIBS), 1)
   test-deps += tests/plugins/libplugintest.$(SO_EXT)