Move writing of the event log to the FS background service

[skliper]

Is your feature request related to a problem? Please describe.
Writing the event log could take a while and is done in the EVS context by command:

cFE/modules/evs/fsw/src/cfe_evs_log.c

Lines 126 to 136 in e80aae9

	/*
	** Function Prologue
	**
	** Function Name: CFE_EVS_WriteLogDataFileCmd
	**
	** Purpose: This routine writes the contents of the internal event log to a file
	**
	** Assumptions and Notes:
	**
	*/
	int32 CFE_EVS_WriteLogDataFileCmd(const CFE_EVS_WriteLogDataFileCmd_t *data)

Describe the solution you'd like
Move to the FS background service like the rest of the logs

Describe alternatives you've considered
None

Additional context
Code review

Requester Info
Jacob Hageman - NASA/GSFC

[skliper]

Might benefit from the general solution to #1473 (related to #994)

[skliper]

Note since the semaphore is locked for both file writing and sending events, any task trying to send an event will get held up until the write completes.

[keegan-moore]

This sounds like it could cause serious priority inversion problems. Is there a plan to address this soon?