OPENTHREAD_CONFIG_SRP_CLIENT_BUFFERS_TXT_BUFFER_SIZE macro

@def OPENTHREAD_CONFIG_SRP_CLIENT_BUFFERS_TXT_BUFFER_SIZE Specifies the size (number of bytes) of TXT record value buffer in the SRP client buffers and service pool. This config is applicable only when `OPENTHREAD_CONFIG_SRP_CLIENT_BUFFERS_ENABLE` is enabled.