install: Add support for architecture filtering for kargs

The use case here is that some kernel arguments are architecture
specific, such as the `console=` kargs. This allows a generic base
image to default to including arch-specific values post install.

`EnvProperties` struct to allow for conditional merging of kargs
depending on whether the archiecture matches. Future properties such as
`platform.id` can be added in the future.

Signed-off-by: Luke Yang <luyang@redhat.com>

docs/src/man-md/bootc-install-config.md

@@ -25,6 +25,7 @@ The `install` section supports two subfields:
    The first value specified will be the default.  To enable both, use `block = ["direct", "tpm2-luks"]`.
 - `filesystem`: See below.
 - `kargs`: An array of strings; this will be appended to the set of kernel arguments.
+- `match_architectures`: An array of strings; this filters the install config.
 
 # filesystem