Determine logical execution time (LET) for each reaction based on immediate downstream

[hokeun]

Reference suggested by @Soroosh129 :

lingua-franca/org.lflang/src/org/lflang/generator/ReactionInstance.java

Line 163 in 3a1f550

for (VarRef effect : definition.getEffects()) {

[hokeun]

@Wonseo-C volunteered to work on this task. And I'll be helping him in case he has any questions. @CloverCho for your information.

[hokeun]

Assigned to myself because this cannot be assigned to @Wonseo-C as he's not a member of this repo yet.

[Wonseo-C]

timer t(0, 100 msec);

logical action a(60 msec):int;
logical action b(40 msec):int;

input x:int;
output y:int;

state count:int(0);

reaction(t) -> y, a, b {=
   	lf_set(y, self->count);
   	self->count++;
	lf_schedule_int(a, 0, 0);
	lf_schedule_int(b, 0, 0);
=}

Look at this pr. #1277.
I fix the code to use Timevalue rather than its magnitude. (advised by @Soroosh129 )

Then, I tried to experiment with getting the minimum delay.
In this code, I get 40 ms in "this.LET"

[Soroosh129]

@Wonseo-C perhaps it would make sense to add some sort of tests for the newly added getLET()?

[Wonseo-C]

@Soroosh129 Sure! But I saw that there is some test error for my PR.

CI / py-tests / run (windows-latest) (pull_request)

[Soroosh129]

This looks like a transient error in SSL. It should go away with a re-run.

[Wonseo-C]

The final work is on the #1292.