Based on the discussion in #1734, we should:

• Add a newtype wrapper: pub struct AccountComponentCode(Library). We'd also want this to be convertible from and to Library.
• Change AccountComponent to contain AccountComponentCode instead of Library. This is so we can return that type from its getters instead of Library. Otherwise, that type would internally be used as a Library.
• Add ScriptBuilder::compile_component_code, which may look like this:

pub fn compile_component_code(
    self,
    component_path: impl AsRef<str>, // <- e.g. `my_account::my_module`
    component_code: impl AsRef<str>, // <- the MASM code
) -> Result<AccountComponentCode, ScriptBuilderError> { ... }

• Replace usages of TransactionKernel::assembler (and its variants) with ScriptBuilder. The goal is to be able to remove all variants of TransactionKernel::assembler after this.
• Rename ScriptBuilder (and ScriptBuilderError) accordingly. Potential names:
  • TransactionAssembler
  • ProtocolAssembler
  • CodeBuilder
• Potentially rename compile_* methods into parse_*, to be in line with the Compile trait rename to Parse from Miden VM - though some discussion may be needed.

Original discussion: #1734 (comment)