refactor coins_tests

Summary:
From the PR description:
> The last few commits contain significant test refactorings to make coins_tests easier to change in follow-ups.

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> test, refactor: Migrate GetCoinsMapEntry to return MaybeCoin

bitcoin/bitcoin@ca74aa7

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> test: Group values and states in tests into CoinEntry wrappers
>
> Note: that this commit affects the test order, but doesn't change its behavior or coverage otherwise.

bitcoin/bitcoin@d5f8d60

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> test: Validate error messages on fail
>
> The `ccoins_add` and `ccoins_write` tests check the actual exception error messages now instead of just that they fail for the given parameters.
> This enables us testing different exceptions in a more fine-grained way in later changes.

bitcoin/bitcoin@c0b4b2c

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> test, refactor: Remove remaining unbounded flags from coins_tests

bitcoin/bitcoin@0a159f0

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> test, refactor: Compact ccoins_access and ccoins_spend
>
> Also added an extra check for `AccessCoin` in `CheckAccessCoin` to make sure its result is also validated.

bitcoin/bitcoin@50cce20

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This concludes backport of [[bitcoin/bitcoin#30906 | core#30906]]
Depends on D18809

Test Plan: `ninja check`

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D18810

Author: l0rinc