Remove Nano S target

[bigspider]

Removes the Nano S compilation target. Also removes some RAM and code size optimizations that are not longer worth the added code complexity.

The latest Nano S version is kept in the nanos branch.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #262 +/- ## ========================================== Coverage ? 84.77% ========================================== Files ? 17 Lines ? 2187 Branches ? 0 ========================================== Hits ? 1854 Misses ? 333 Partials ? 0 ``` | [Flag](https://app.codecov.io/gh/LedgerHQ/app-bitcoin-new/pull/262/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=LedgerHQ) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/LedgerHQ/app-bitcoin-new/pull/262/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=LedgerHQ) | `84.77% <100.00%> (?)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=LedgerHQ#carryforward-flags-in-the-pull-request-comment) to find out more.

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[sonarcloud[bot]]

Quality Gate failed

Failed conditions
44.4% Coverage on New Code (required ≥ 80%)
E Reliability Rating on New Code (required ≥ A)

See analysis details on SonarCloud

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