Migrating from getExpressionInfo to expression wrappers

[GulgDev]

Continuing the discussion in #7507, here's what has already been decided:

1. getExpressionInfo should be rewritten to just return an object made from the corresponding wrapper.
2. getExpressionInfo should be deprecated and replaced with a function that returns an expression wrapper for an expression of unknown class. Maybe we can make Expression constructor return the specific instance? Can we just make the instruction-building functions return expression wrappers? That shouldn't be a breaking change, as expression wrappers can be implicitly converted to Wasm pointers via valueOf (e.g. +expr or expr | 0).
3. Expression infos and expression wrappers need to be made interchangeable to not make the migration a breaking change.

Is there something else to add or clarify?

[GulgDev]

Opened a PR: #7525