Remove the MBEDTLS_SSL_DTLS_BADMAC_LIMIT config.h option

[mpg]

This option is a trade-off between a feature a code size: it allows people who don't need that feature to avoid paying the cost in code size, by disabling it.

However:

• the code size savings are not that significant
• in the future we can design a mechanism for that an other ssl_config options that will save more code size and be more uniform, see Identify improvements in baremetal branch that should be upstreamed #3535 "Hardcoding of SSL options"

Work to do:

• remove this option and let the code behave as if it was always enabled
• if any tests had a declared dependency on this option, remove that declaration
• in the end git grep MBEDTLS_SSL_DTLS_BADMAC_LIMIT should find no match except in the ChangeLog, the CI should pass and no test will have been removed