refactor: move act/model and act/exprparser to actionslib

Gitea needs the workflow model and the expression evaluator to parse
workflows and to build the task payload this runner consumes, so it had
to depend on gitea.com/gitea/runner for it. Both packages now live in
gitea.dev/actionslib, the module both sides already share, and this
repository consumes them from there.

The GithubContext helpers that need a git checkout on disk (SetRef,
SetSha and SetRepositoryAndOwner) are not moved: they are runner only and
would drag a git client and the act context logger into the shared
module. They become functions of the new act/ghcontext package, together
with their tests.

act/common.CartesianProduct moved to the shared model package as well,
act/model was its only user. act/model/testdata/container-volumes is now
act/runner/testdata/container-volumes, its only user is runner_test.go.

The x-runner-uuid and x-runner-token header names come from
actionslib too, so the runner and Gitea cannot drift apart.

The generated runner API code moved along with the repository, from
gitea.dev/actions-proto-go to gitea.dev/actionslib, so the imports of
ping/v1 and runner/v1 follow the new module path. Both cannot be used at
once: the generated types would no longer be the same types.

Signed-off-by: Lunny Xiao <xiaolunwen@gmail.com>

internal/pkg/client/header.go

@@ -3,7 +3,11 @@
 
 package client
 
+import "gitea.dev/actionslib/pkg/protocol"
+
+// The headers are defined in the shared protocol package so that Gitea and the
+// runner cannot drift apart.
 const (
-	UUIDHeader  = "x-runner-uuid"
-	TokenHeader = "x-runner-token"
+	UUIDHeader  = protocol.UUIDHeader
+	TokenHeader = protocol.TokenHeader
 )