Keep unwrapped self in extensions for optional types

[SimplyDanny]

Resolves #6390.

[SwiftLintBot]

	19 Messages
📖	Building this branch resulted in a binary size of 27204.96 KiB vs 27204.38 KiB when built on main (0% larger).
📖	Linting Aerial with this PR took 0.77 s vs 0.77 s on main (0% slower).
📖	Linting Alamofire with this PR took 1.03 s vs 0.99 s on main (4% slower).
📖	Linting Brave with this PR took 6.84 s vs 6.83 s on main (0% slower).
📖	Linting DuckDuckGo with this PR took 22.73 s vs 22.74 s on main (0% faster).
📖	Linting Firefox with this PR took 11.04 s vs 11.01 s on main (0% slower).
📖	Linting Kickstarter with this PR took 7.66 s vs 7.7 s on main (0% faster).
📖	Linting Moya with this PR took 0.42 s vs 0.4 s on main (4% slower).
📖	Linting NetNewsWire with this PR took 2.3 s vs 2.28 s on main (0% slower).
📖	Linting Nimble with this PR took 0.68 s vs 0.66 s on main (3% slower).
📖	Linting PocketCasts with this PR took 7.13 s vs 7.14 s on main (0% faster).
📖	Linting Quick with this PR took 0.44 s vs 0.42 s on main (4% slower).
📖	Linting Realm with this PR took 3.23 s vs 3.25 s on main (0% faster).
📖	Linting Sourcery with this PR took 1.84 s vs 1.78 s on main (3% slower).
📖	Linting Swift with this PR took 4.35 s vs 4.32 s on main (0% slower).
📖	Linting SwiftLintPerformanceTests with this PR took 0.32 s vs 0.31 s on main (3% slower).
📖	Linting VLC with this PR took 1.1 s vs 1.1 s on main (0% slower).
📖	Linting Wire with this PR took 17.27 s vs 17.29 s on main (0% faster).
📖	Linting WordPress with this PR took 11.48 s vs 11.43 s on main (0% slower).

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