fix(modifier_order): recognize isolated isolation modifier

[wyf027]

Summary

• Map the isolated declaration modifier to the existing isolation modifier group in modifier_order.
• Users can now order isolated via isolation in preferred_modifier_order, consistent with nonisolated.

Fixes #6164

Test plan

• Extended testIsolationModifierOrder with isolated non-triggering/triggering/correction examples
• CI (Buildkite)

[SwiftLintBot]

	19 Messages
📖	Building this branch resulted in the same binary size as when built on main.
📖	Linting Aerial with this PR took 0.8 s vs 0.83 s on main (3% faster).
📖	Linting Alamofire with this PR took 1.12 s vs 1.09 s on main (2% slower).
📖	Linting Brave with this PR took 7.43 s vs 7.39 s on main (0% slower).
📖	Linting DuckDuckGo with this PR took 29.91 s vs 29.92 s on main (0% faster).
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📖	Linting Moya with this PR took 0.46 s vs 0.48 s on main (4% faster).
📖	Linting NetNewsWire with this PR took 2.92 s vs 2.89 s on main (1% slower).
📖	Linting Nimble with this PR took 0.69 s vs 0.69 s on main (0% slower).
📖	Linting PocketCasts with this PR took 8.21 s vs 8.26 s on main (0% faster).
📖	Linting Quick with this PR took 0.47 s vs 0.46 s on main (2% slower).
📖	Linting Realm with this PR took 3.0 s vs 3.02 s on main (0% faster).
📖	Linting Sourcery with this PR took 1.91 s vs 1.91 s on main (0% slower).
📖	Linting Swift with this PR took 4.82 s vs 4.86 s on main (0% faster).
📖	Linting SwiftLintPerformanceTests with this PR took 0.3 s vs 0.35 s on main (14% faster).
📖	Linting VLC with this PR took 1.27 s vs 1.27 s on main (0% slower).
📖	Linting Wire with this PR took 19.32 s vs 19.27 s on main (0% slower).
📖	Linting WordPress with this PR took 13.07 s vs 13.05 s on main (0% slower).

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[SimplyDanny]

Superseded by #6759.