This commit refactors some of the functions of
sample signing module. Mainly convert clones
into references, which helps to avoid extra
memory copies when executing

Signed-off-by: Xynnn007 <[email protected]>

This commit brings in KBS Resource URI support.
All the functions related to read a file from
given uri has been brought to module `resource`.

Now different resources can be fetched using the
overall api resource::get_resource()

This Api now support two basic protocol:
- file://  read file from local filesystem
- kbs:// read file from KBS

This commit also fixes features of `keywrap-grpc`,
`keywrap-ttrpc` and `keywrap-native` to let them
to be allowed to exist at the same time.

Signed-off-by: Xynnn007 <[email protected]>

This commit bring out the sigstore configuration file
into ImageClient's config to specify which sigstore
configuration file for simple signing will be used.

Also, some refactoring is applied on the simple signing
related codes, including:
- Now when merging two sigstore configs, if the contents
are duplicated but not conflict, no error will be raised

Besides, `KeyPath` field in both cosign and simple signing
will use either kbs resource uri or local filesystem path
from now on. If a local fs path is used, a absolute path
is recommended

Signed-off-by: Xynnn007 <[email protected]>

Credential in integration test now is specified
by a kbs resource uri (kbs resource uri in
`get_resource` api test)

Image decryption key in integration is specified
by a kbs resource uri in image's AnnotationPacket
(kbs resource uri in `unwrap_key` api test)

Signed-off-by: Xynnn007 <[email protected]>

Signed-off-by: Xynnn007 <[email protected]>

Signed-off-by: Xynnn007 <[email protected]>

The env should be removed first and then the config be
inited, or when the env CC_IMAGE_WORK_DIR is set, the first
assert_eq will fail

Signed-off-by: Xynnn007 <[email protected]>

related rev brings kbs resource uri scheme

Signed-off-by: Xynnn007 <[email protected]>