Replace simple if let constructs with Option::map

[LingMan]

Replaces a few constructs of the form

if let Some(x) = var {
    Some(...)
} else {
    None
}

with calls to Option::map.

@rustbot modify labels +C-cleanup +T-compiler

[rust-highfive]

r? @ecstatic-morse

(rust-highfive has picked a reviewer for you, use r? to override)

[lcnr]

r? @lcnr

@bors r+ rollup

[bors]

📌 Commit af9402a has been approved by lcnr

[bors]

⌛ Testing commit af9402a with merge 5e6e1e3...

[bors]

☀️ Test successful - checks-actions
Approved by: lcnr
Pushing 5e6e1e3 to master...