feat(boil): Support for per-image build arguments

[Techassi]

I noticed in #1600 that we need to copy+paste many build arguments (with the same value) across versions of the same image in the boil-config files. In order to make this easier, it is now possible to specify a shared list of build arguments which apply to all versions of a single image.

# Set it here once instead of having to set it for every version individually below.
[build-arguments]
golang-version = "1.26.0"

# Version 1.12.3
[versions."1.12.3".local-images]
stackable-devel = "1.0.0"
vector = "0.55.0"

# Version 1.16.2
[versions."1.16.2".local-images]
stackable-devel = "1.0.0"
vector = "0.55.0"

The arguments can be overwritten on a per-version basis if needed.

[dervoeti]

This feature currently doesn't allow overwriting the value on a per version level.

We need this to be in this PR I'd say because currently overwriting makes the build fail:

head -n13 opa/boil-config.toml
[metadata.registries]
"oci.stackable.tech" = { namespace = "sdp" }

[build-arguments]
golang-version = "9.9.9"

# Version 1.12.3
[versions."1.12.3".local-images]
stackable-devel = "1.0.0"
vector = "0.55.0"

[versions."1.12.3".build-arguments]
golang-version = "1.26.0"

cargo boil build opa=1.12.3
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.11s
     Running `target/debug/boil build opa=1.12.3`
[+] Building 0.0s (1/1) FINISHED                                                                                                                                                     docker:default
 => [internal] load local bake definitions                                                                                                                                                     0.0s
 => => reading from stdin 4.64kB                                                                                                                                                               0.0s
-.json:1
--------------------
   1 | >>>
--------------------
ERROR: -.json:1,987-1003: Duplicate object attribute; An attribute named "GOLANG_VERSION" was already defined at -.json:1,961-977.
Error: failed to run build command

Which is probably even better than silently ignoring it, but I would still include that functionality in this PR already.

Cool feature though, makes the boil configs more readable 🙂

[Techassi]

We need this to be in this PR I'd say because currently overwriting makes the build fail

Your wish has been granted in 1b0ce2d :)

[dervoeti]

Change itself LGTM, two optional things:

• Update README.md
• The build arguments in the global config (src/config.rs) should probably get
  #[serde(default, deserialize_with = "docker::deserialize_args")] as well

[Techassi]

Both very valid points. On it!

EDIT: Both addressed in a5ccbd2 and 6e856bc.

[dervoeti]

ship it