fix(core): validate op buffer backing stores

[nathanwhit]

This updates op2 buffer conversion so generated ops do not borrow slices from backing stores whose address or concurrency properties can change.

Read-only shared and resizable inputs are snapshotted before dispatch, preserving ordinary input behavior. Mutable, retained, and raw-pointer mappings reject those stores because copying would change their mutation or ownership contract. Detach-mode buffers keep their existing ownership-transfer path.

The fast and slow dispatch paths now apply the same rules. Regression coverage exercises shared and resizable typed arrays, ArrayBuffers, DataViews, retained buffers, raw pointers, copy-mode inputs, and Node isUtf8/isAscii compatibility.

Tests:

• cargo test -p deno_ops
• cargo test -p deno_core
• cargo test -p unit_node_tests --test unit_node -- buffer_test
• cargo clippy -p deno_core -p deno_ops --all-targets -- -D warnings
• ./tools/format.js --check
• ./tools/lint.js --js