Corrupt ALP-RD, RLE and RunEnd metadata can panic a file read #10756

What happened?

Several deserialize implementations trust their stored metadata, so a corrupt or crafted file can make a read panic instead of returning an error. The clearest case is ALP-RD: ALPRD::deserialize slices the stored dictionary with the stored dict_len without a bounds check (encodings/alp/src/alp_rd/array.rs:184).

Steps to reproduce

Call ALPRD.deserialize for an f32 array of length 1 with two children (buffer![0u16] and buffer![0u32]) and this metadata:

ALPRDMetadata {
    right_bit_width: 32,
    dict_len: 8,
    dict: vec![0, 1],
    left_parts_ptype: PType::U16 as i32,
    patches: None,
}

panicked at encodings/alp/src/alp_rd/array.rs:185:13:
range end index 8 out of range for slice of length 2

Expected: a Serde error.

Environment

develop at 3974ee069c, run as a unit test in vortex-alp.

Additional context

Other read paths can panic for the same reason. These come from reading the code and were not run:

• ALP-RD accepts a dictionary with more than MAX_DICT_SIZE (8) entries, and the alp crate panics on such a dictionary when it decodes (alp-0.0.4/src/alp_rd/mod.rs:373).
• ALP-RD does not check the left-part codes against the dictionary length. scalar_at (encodings/alp/src/alp_rd/ops.rs:42) and the patched decode path index the dictionary with each code.
• ALP-RD checks only that right_bit_width fits a u8, not that it is below the bit width of the float, so the decode shift can overflow (ops.rs:54, :63).
• ALP-RD accepts any unsigned left_parts_ptype, but execute reads the left parts with into_buffer_mut::<u16>() (array.rs:285, :297).
• RLE calls dtype.as_ptype() in deserialize (encodings/fastlanes/src/rle/vtable/mod.rs:172), which panics for a non-primitive dtype.
• RunEnd converts num_runs and offset with vortex_expect (encodings/runend/src/array.rs:156, :160), which panics on 32-bit targets for values above usize::MAX.

Most of these are cheap metadata checks in deserialize or validate. The code bound for ALP-RD needs either a scan of the left parts or a checked lookup when decoding. Found while reviewing #10755.