stage2: add debug info for payload captures + inline function parameters

[Vexu]

This add dbg_block_{begin,end} which control visibility of debug info variables:

pub fn main() void {
    {
        var a: u32 = undefined;
        a = 0;
    }
    {
        var a: u32 = undefined;
        a = 1;
        @breakpoint();
        // p a
        // before: 0
        // after: 1
    }
}

Fixes #7239 for stage2.