[sdk] gen_sdk language args should preserve values containing '='

Environment

• KubeVela master
• SDK generator: pkg/definition/gen_sdk

Reproduction

Pass a language argument whose value contains =:

langArgs := []string{GoProxy=https://proxy.example.com?a=b}
args, err := NewLanguageArgs(go, langArgs)

Current behavior

The parser rejects the argument because it splits on every = and expects exactly two parts.

Expected behavior

The parser should treat the first = as the separator and preserve the rest of the value, so the example above is parsed as:

GoProxy -> https://proxy.example.com?a=b

Why this matters

The current implementation makes it impossible to pass through language-argument values that naturally contain = characters.