Fix manual_map and manual_filter FN for complex map body

[profetia]

Closes #16776

Inspired by the original reproducer in #16751. After this PR the two lints no longer require the map/filter body to be a single expression of map/filter.

changelog: [manual_map] fix FN for complex map body
changelog: [manual_filter] fix FN for complex map body

[rustbot]

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[github-actions]

Lintcheck changes for b5e1670

Lint	Added	Removed	Changed
clippy::manual_map	10	0	1

This comment will be updated if you push new changes

[profetia]

Also closes #16776 in this PR

[profetia]

I feel that manual_filter.rs, manual_map.rs and manual_utils.rs can be merged into one, since we are implementing filter, map and and_then (i.e. filter map).