Energetic particle confinement proxies Gamma_delta, Gamma_alpha

[rahulgaur104]

I thought there was an issue taking about it but could not find it.
Bounce averaging functionality is now complete so we can easily implement Gamma alphabet soup form Velasco's paper.

Gamma_c is already available in master.

[dpanici]

https://github.com/PlasmaControl/DESC/tree/rg/otherGammas

[unalmis]

rg/otherGammas is not correct. I suggest using #2220.