Key store manager+FileSystem.h simulator

[deuxksix]

This PR does two things:

1. add support of src/system/physical/fileSystem.h in simulator
2. add abstraction to give everyone access to the common key-value store

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Users may discover new static methods in their mode context:

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There are pointers to the KeyProxy class which describes a typical use case:

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Others may discover these functionnalities through the basic mode documentation:

Note: intentionally, we try to orient users into using the custom ramp & index, more basic & less error-prone!

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Other ways to discover direct access to the key-value store system is through its namespace:

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Several remarks:

1. accessing key / values by "name" hashes the key name on the 31 lower-significant bits, prone to collisions
2. all other keys starts with a one, with the next 15 bits partitioning the key space in way to avoid collisions
3. the manager, each group and each mode have all their own uint16_t key space, indexed with enumerations
4. each space has a storeId serial, used to detect when groups / modes changes, dropping "obsolete" keys
5. values up to 64 bytes in size are transparently stored on several keys, only when using indexed key spaces

And as a bonus, at last, the lamp now remembers what was its last mode, its ramp value, other favorites, etc

Draft: I still need to validate that everything works on real hardware!

[deuxksix]

draft status removed

now tested with a couple issues solved

[BaptisteHudyma]

Looks awesome thanks!!!
I will test it on several hardware before merge

[deuxksix]

rebased +also fixed a bug

Note: it could be cool at some point to have explicit enter_mode / quit_mode / enter_group / quit_group handlers because right now, as there are several ways to enter / quit things (turn on, turn off, next group, next mode, favorite, etc) it's easy to forget to load / save something when writing bugs (see save_ramps called in three distinct places)

[BaptisteHudyma]

Tested and approved, congrats <3