19460: cpu/stm32/usbdev_fs: fix ep registration and EP_REG assignments r=gschorcht a=dylad

### Contribution description
This PR provides two fixes for the `usbdev_fs` driver:

- Fix endpoints registration
- Fix assignment of toggleable bits in EP_REG(x) registers

These bugs were encountered with the USBUS MSC implementation.

Regarding the endpoints registration:

For the `usbdev_fs` peripheral, IN and OUT endpoints of the same index must have the same type.
For instance, if EP1 OUT is a bulk endpoint, EP1 IN must either be unused or used as bulk too but it cannot be used as interrupt or isochronous.
With the previous check, the following registration pattern (EP OUT Bulk -> EP IN Interrupt -> EP IN Bulk) would assign both EP OUT Bulk and EP IN Interrupt to same endpoint index. So the configuration would be broken.
Applying the same registration pattern with this patch would now produce EP OUT Bulk -> 1 / EP IN Interrupt -> 2 / EP IN Bulk 1. Which is a working configuration for this IP.

and for the second fix:

EP_REG(x) registers have a total of 6 toggleable bits. Those bits can only be toggled if we write a one to it, otherwise writing a zero has no effect
This commit fixes all the access to these registers to prevent from modifying these bits when not needed.
Without this patch, the endpoint status (VALID / NACK / STALL) can be erroneously modify because bits are not cleared when assigning the new content to the register and thus make the bits toggle and change values.

### Testing procedure
This can be tested with tests/usbus_msc on any board using this `usbdev_fs` driver.
It is easier to test this PR with #19443 alongside. Then the following would be enough:
`CFLAGS='-DSECTOR_COUNT=64' USEMODULE='mtd_emulated' make -j8 BOARD=p-nucleo-wb55 -C tests/usbus_msc flash`

Otherwise this can also be tested by attaching a SPI<->SDCARD adapter.

### Issues/PRs references
None.

Co-authored-by: Dylan Laduranty <[email protected]>

19443: drivers: add support for MTDs emulated in RAM r=dylad a=gschorcht

### Contribution description

This PR adds a driver to provide MTDs that are emulated in RAM. It allows to test MTD-based applications on boards that do not provide MTDs by hardware.

It includes also some small documentation fixes for `mtd.h` that were found while writing the driver.

### Testing procedure

The following tests should work on any board:

`tests/pkg_littlefs`
`tests/pkg_littlefs2`
`tests/pkg_spiffs`

### Issues/PRs references


Co-authored-by: Gunar Schorcht <[email protected]>

19465: drivers/mtd: use XFA for pointers to defined MTDs r=benpicco a=gschorcht

### Contribution description

This PR provides the support to hold pointers to defined MTDs within a XFA. The XFA allows
- to access MTDs of different types (`mtd_flashpage`, `mtd_sdcard`, `mtd_emulated`, ...) by an index
- to determine the number of MTDs defined in the system.

### Testing procedure

To be defined once PR #19443 is merged because emulated MTDs will allow to test this PR on arbitrary boards.

### Porting Guide

For external boards:
 - remove the `MTD_NUMOF` definition from `board.h`
 - add `MTD_XFA_ADD(<mtd_dev>, <idx>);` to the definition of `<mtd_dev>`.
 - `MTD_0`, `MTD_1`, … defines are no longer needed.

### Issues/PRs references

 Related to PR #19443

19981: Fletcher32: Add incremental API r=benpicco a=bergzand

### Contribution description

This PR extends the current fletcher32 checksum with an incremental API mode. This way the bytes to be checksummed can be supplied via multiple successive calls and do not have to be provided in a single consecutive buffer.

I've also rephrased the warning with the original function a bit as that function uses an `unaligned_get_u16` to access the data. The data thus does not require alignment, but the length does need to be supplied as number of 16 bit words.

### Testing procedure

The test has been extended


### Issues/PRs references

None

19995: sys/psa_crypto: Fix macro for public key max size and SE example r=benpicco a=Einhornhool

### Contribution description
#### 1. Wrong public key size when using secure elements, introduced by  #19954
Fixed conditions for key size macros in `crypto_sizes.h`.

#### 2. EdDSA and ECDSA examples fail when using a secure element because of unsopported changes introduced by #19954
Updated `example/psa_crypto` to use only supported functions for secure elements.

### Testing procedure
Build `example/psa_crypto` for secure elements and run application

Output on master:
```
2023-10-19 14:33:24,372 # main(): This is RIOT! (Version: 2019.07-devel-22378-gb6772)
2023-10-19 14:33:24,372 # HMAC SHA256 took 56393 us
2023-10-19 14:33:24,372 # Cipher AES 128 took 68826 us
2023-10-19 14:33:24,372 # *** RIOT kernel panic:
2023-10-19 14:33:24,373 # HARD FAULT HANDLER
2023-10-19 14:33:24,373 # 
2023-10-19 14:33:24,373 # *** rebooting...

```
Output with fixes:
```
2023-10-19 13:35:24,715 # main(): This is RIOT! (Version: 2019.07-devel-22384-g8ef66-dev/psa-crypto-fixes)
2023-10-19 13:35:24,715 # HMAC SHA256 took 56374 us
2023-10-19 13:35:24,715 # Cipher AES 128 took 68805 us
2023-10-19 13:35:24,715 # ECDSA took 281164 us
2023-10-19 13:35:24,715 # All Done
```


Co-authored-by: Gunar Schorcht <[email protected]>
Co-authored-by: Koen Zandberg <[email protected]>
Co-authored-by: Lena Boeckmann <[email protected]>