feat: draw PID limit boxes on eta vs. P plot in CI

[c-dilks]

Briefly, what does this PR introduce?

Draw PID (eta,p) limit boxes on eta vs. P histogram (CI artifact)

What kind of change does this PR introduce?

• Bug fix (issue #__)
• New feature (issue #__)
• Documentation update
• Other: __

Please check if this PR fulfills the following:

• Tests for the changes have been added
• Documentation has been added / updated
• Changes have been communicated to collaborators

Does this PR introduce breaking changes? What changes might users need to make to their code?

no

Does this PR change default behavior?

no

[c-dilks]

@chchatte92 could you update the p and eta ranges for the dRICH? So far I just put in some rough guesses:

epic-analysis/macro/ci/postprocess_eta_vs_p_forPID.C

Lines 13 to 32 in 7d2d887

	limits.push_back({
	"#splitline{dRICH}{gas}",
	new TBox(
	9.5, // p min
	1.3, // eta min
	50.0, // p max
	3.7 // eta max
	),
	kRed
	});
	limits.push_back({
	"#splitline{dRICH}{aerogel}",
	new TBox(
	2.0, // p min
	1.3, // eta min
	10.3, // p max
	3.7 // eta max
	),
	kBlue
	});

And here's what it looks like (with very low statistics):

[c-dilks]

Perhaps with the help of @preghenella, et al., we could add the other PID subsystems too.

[chchatte92]

@c-dilks, we will do that. BTW, with Q2>1; p_T>0.1 and 0.01<y<0.95 positive pions are like this:

This means the complete separation (both species positively identified) of pi/K at eta=1.5 will mostly be coming from aerogel and gas will be just for vetoing. But, I remember around eta=1.5, we will have no more the aerogel ring. Won't we?

[c-dilks]

But, I remember around eta=1.5, we will have no more the aerogel ring. Won't we?

DRICH_zmin                     =      195.000
DRICH_snout_length             =       20.000
DRICH_rmax1                    =      104.656

Aerogel minimum eta:

[c-dilks]

BTW, you can find the updated (eta,p) plots in artifact _FULL_RESULTS under eta_vs_p_forPID.Ele.