Signed-off-by: CarlOlsson <carlolsson.co@gmail.com>

This is a step towards isolating time from the system.

_subscriptions is a vector that is resized when needed. However there could
still be references to elements in the vector when the resize happens.
These references then become invalid.
Using a vector of pointers fixes that.

 - px4_add_module now requires MAIN
 - px4_add_library doesn't automatically link

_uorb_topics_list was marked as 'const char *' array, which means the data
of the array was not actually const and thus landed in the data section
(so in RAM instead of FLASH).
The size of the array is 436 bytes.

This got introduced the the addition of the perf counter to the log.

Fixes the error:
unknown log message type 73

Just to make sure that it will never be used on NuttX. This is not an
architectural limitation, just a memory optimization, since we call
clearenv() on NuttX.

The error counter is an indicator that the logger missed samples or dropped
due to a too small write buffer.

in preparation to the updated ekf2 replay

This could happen and then the sleep duration would wrap and be huge.

This only applies parameters from the log file and user-supplied overrides.
It is intended to be called as one of the first startup commands (after
param load), so that during startup, all applications find the parameters
from the replayed system.

Note that this is an optional command and 'replay start' will again load
and apply the parameters in any case.

This adds a new module that does:
- read an parse an ULog file, given via ENV variable 'replay'
- apply all parameters from the log file
- read and apply user-defined override parameters from a file
- publish all messages in 'real-time' from the log file and add a constant
  offset to the timestamp to match the system time.
- apply changed parameters in the log (which are not overridden)