Forbid memcpyopt if the source pointer escapes

[ironcev]

Description

This PR fixes the issue of the source pointer not being checked for escapes in the memcpyopt::local_copy_prop_prememcpy. E.g., in this example:

script {
    entry fn main() -> u64 {
        local u64 x
        local u64 y

        entry():
        v0 = get_local ptr u64, x
        v1 = get_local ptr u64, y
	
        v2 = load v0
        v3 = call escape(v0) // `v0` escapes here.
        store v2 to v1
        v4 = load v1

        ret u64 v4
    }

    fn escape(a: ptr u64) -> u64 {
        entry(a: ptr u64):
        z = const u64 0
        store z to a
        ret u64 z
    }
}

after the memcpyopt the store v2 to v1 got optimized away and the final return was from v0. It means the returned value was the one changed in escape and not the one taken before the call to escape.

Checklist

• I have linked to any relevant issues.
• I have commented my code, particularly in hard-to-understand areas.
• I have updated the documentation where relevant (API docs, the reference, and the Sway book).
  • If my change requires substantial documentation changes, I have requested support from the DevRel team
• I have added tests that prove my fix is effective or that my feature works.
• I have added (or requested a maintainer to add) the necessary Breaking* or New Feature labels where relevant.
• I have done my best to ensure that my PR adheres to the Fuel Labs Code Review Standards.
• I have requested a review from the relevant team or maintainers.