Use semver manifests as kustomize base

Instead of cloning the components repositories to download the base manifests, we build them in CI at release time and download them in tk install/bootstrap based on the provided semver. This speeds up the manifests generation from minutes to milliseconds.

docs/cmd/tk_bootstrap.md

@@ -11,7 +11,7 @@ The bootstrap sub-commands bootstrap the toolkit components on the targeted Git
 ```
       --components strings   list of components, accepts comma-separated values (default [source-controller,kustomize-controller,helm-controller,notification-controller])
   -h, --help                 help for bootstrap
-  -v, --version string       toolkit tag or branch (default "master")
+  -v, --version string       toolkit version (default "latest")
 ```
 
 ### Options inherited from parent commands

docs/cmd/tk_bootstrap_github.md

@@ -59,7 +59,7 @@ tk bootstrap github [flags]
       --namespace string     the namespace scope for this operation (default "gitops-system")
       --timeout duration     timeout for this operation (default 5m0s)
       --verbose              print generated objects
-  -v, --version string       toolkit tag or branch (default "master")
+  -v, --version string       toolkit version (default "latest")
 ```
 
 ### SEE ALSO

docs/cmd/tk_bootstrap_gitlab.md

@@ -55,7 +55,7 @@ tk bootstrap gitlab [flags]
       --namespace string     the namespace scope for this operation (default "gitops-system")
       --timeout duration     timeout for this operation (default 5m0s)
       --verbose              print generated objects
-  -v, --version string       toolkit tag or branch (default "master")
+  -v, --version string       toolkit version (default "latest")
 ```
 
 ### SEE ALSO

docs/cmd/tk_install.md

@@ -15,10 +15,10 @@ tk install [flags]
 
 ```
   # Install the latest version in the gitops-systems namespace
-  tk install --version=master --namespace=gitops-systems
+  tk install --version=latest --namespace=gitops-systems
 
   # Dry-run install for a specific version and a series of components
-  tk install --dry-run --version=0.0.1 --components="source-controller,kustomize-controller"
+  tk install --dry-run --version=v0.0.7 --components="source-controller,kustomize-controller"
 
   # Dry-run install with manifests preview 
   tk install --dry-run --verbose
@@ -36,7 +36,7 @@ tk install [flags]
       --export               write the install manifests to stdout and exit
   -h, --help                 help for install
       --manifests string     path to the manifest directory, dev only
-  -v, --version string       toolkit tag or branch (default "master")
+  -v, --version string       toolkit version (default "latest")
 ```
 
 ### Options inherited from parent commands