Include correct layer weights for v15 ECAL

[tvami]

I am updating ldmx-sw, here are the details.

What are the issues that this addresses?

Resolves https://github.com/LDMX-Software/ldmx-sw/issues/1850

Having it as draft, since I want my students to measure the secondary correction too if we are there already

Check List

• [x] I successfully compiled ldmx-sw with my developments.
• [x] I read, understood and follow the coding rules.

• [x] I ran my developments and the following shows that they are successful.

I ran the ecal CI and it technically works

[tvami]

We've tried a few things, see the attached PDF. For now I think this is good enough, at least this will bring the energy centered around 8 GeV for the 8 GeV gun. We have some plans for making things better, but I'm happy enough with this to be merged LDMX_UCSB_xiaoyun_wu.pdf

[tvami]

The money plot: