Switch to compose state and kotlin flows - 1. iteration (#279)

* Added `forceDarkModeFlow`

Signed-off-by: Arnau Mora Gras <arnyminerz@proton.me>

* Deprecated method

Signed-off-by: Arnau Mora Gras <arnyminerz@proton.me>

* Added test

Signed-off-by: Arnau Mora Gras <arnyminerz@proton.me>

* Added comments

Signed-off-by: Arnau Mora Gras <arnyminerz@proton.me>

* Migrated to flow

Signed-off-by: Arnau Mora Gras <arnyminerz@proton.me>

* Migrated to flow

Signed-off-by: Arnau Mora Gras <arnyminerz@proton.me>

* Fixed deprecations

Signed-off-by: Arnau Mora Gras <arnyminerz@proton.me>

* Made all functions suspending

Signed-off-by: Arnau Mora Gras <arnyminerz@proton.me>

* Fixed suspending calls

Signed-off-by: Arnau Mora Gras <arnyminerz@proton.me>

* Made callbacks suspending

Signed-off-by: Arnau Mora Gras <arnyminerz@proton.me>

* Fixed tests

Signed-off-by: Arnau Mora Gras <arnyminerz@proton.me>

* Added missing overrides

Signed-off-by: Arnau Mora Gras <arnyminerz@proton.me>

* Remove unnecessary close calls

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Signed-off-by: Arnau Mora Gras <arnyminerz@proton.me>
Co-authored-by: Sunik Kupfer <kupfer@bitfire.at>