Refactor parser

[gauravgahlot]

• The parser should be able to parse all the section at once.
• The function parse_sections should return a structure like

pub(crate) struct Sections {
    pub types: Vec<u8>,     // Raw type section payload
    pub functions: Vec<u8>, // Raw function section payload
    pub exports: Vec<Export>, // Parsed exports
    pub funcs: Vec<Func>,   // Parsed function bodies
    // Other sections...
}

• This would mean we shouldn’t change its structure but instead work within this framework.