Add option to use display_force_sw_blink in msp displayport

[mmosca]

rebased to release_7.1.0

Looks like some MSP DisplayPort implementaions have bugs related to the blink attribute.

Allow a user to force software emulation of the blink attribute by using set display_force_sw_blink = true on the cli.

Fixes #9552

Replaces #9625

[Jetrell]

@mmosca I went back over this and did some more comprehensive testing. By adding many different numbers of OSD element to the display.

In my original test. I only took the character count into the mid thirties, thinking that would be extreme. And it worked.
But I have found a region it reverts back to a slower blinking rate. When between 21 to 28 elements are added to the displayed.

[mmosca]

@mmosca I went back over this and did some more comprehensive testing. By adding many different numbers of OSD element to the display.

In my original test. I only took the character count into the mid thirties, thinking that would be extreme. And it worked. But I have found a region it reverts back to a slower blinking rate. When between 21 to 28 elements are added to the displayed.

Can you check if the osd task is running late? or try increasing the refresh time for the osd? Does changing the osd_msp_displayport_fullframe_interval values affect the result in the 21-28 range?

[0crap]

I tested this PR.

The issue I was having is that inflight tuning was not possible, because when selecting an item it didn't blink but just went to "off". (Or blink very irregular.)
So I could not see what the actual value of the item was.
Problem is I can't reproduce the issue on 7.0.0, I guess because on the bench my Walksnail digital system has close to no delay.
During flight that goes up and probably shows the issue.
Anyway, flashing this PR shows the selected tuning item blinking nicely. (So no regression issues found.)

I can't fly atm because it's mid winter, so I can't tell if my issue is fixed by this PR.
Sorry for that.

set display_force_sw_blink = ON or OFF makes no difference on my setup.
Tested on a MATEKH743 (V2)

version
INAV/MATEKH743 7.1.0 Jan 10 2024 / 00:01:37 (fe3a04a)
GCC-10.3.1 20210824 (release)