Build fixes and warning fixes

[OvermindDL1]

Made the project build without warnings (and resisted the urge to enable deprecated and unchecked warnings, there are so many...) as on my system warnings are errors by default so I just couldn't build.

Also updated gradle.

Also added dev and sources tasks and set up the uploadArchives task to use external configuration for uploads.

I did minor testing but please build and test on your own before merging.

[jrddunbr]

Running through CI/CD server: https://teamcity.vars.ja4.org/buildConfiguration/ElectricalAge_Build/11?hideProblemsFromDependencies=false&hideTestsFromDependencies=false&expandBuildChangesSection=true

[OvermindDL1]

Made COFH required at runtime via gradle, and added another comment for possible later use of more and better warnings.

Probably worth just going to RFG though if much more is done.

[jrddunbr]

Building in new commit and testing: https://teamcity.vars.ja4.org/buildConfiguration/ElectricalAge_Build/12?hideProblemsFromDependencies=false&hideTestsFromDependencies=false&expandBuildChangesSection=true

[jrddunbr]

Crashes in playtesting with a standalone client:

[18:21:08] [Client thread/ERROR] [FML]: Caught exception from Eln
java.lang.NoSuchFieldError: water
    at mods.eln.fluid.ElnFluidRegistry.<clinit>(ElnFluidRegistry.kt:18) ~[ElnFluidRegistry.class:?]

https://github.com/age-series/ElectricalAge/blob/8bd022656e40a64950e01840e627d2cc99e813ab/src/main/java/mods/eln/fluid/ElnFluidRegistry.kt#L18

[jrddunbr]

This works now, but I think we're going to close this in favor of #282

[jrddunbr]

Effectively merged into 1.21.x