Add fuel-core-keygen to dockerfile.

[wengych]

Description

Add fuel-core-keygen binary to docker image.

[fuel-cla-bot]

Thanks for the contribution! Before we can merge this, we need @wengych to sign the Fuel Labs Contributor License Agreement.

[AurelienFT]

Hello @wengych, what's the rationale behind this change ?

[wengych]

Hello @wengych, what's the rationale behind this change ?

I was trying deploy fuel node to docker, and found fuel-core-keygen binary is missing.

[rymnc]

@wengych please create a changelog entry in CHANGELOG.md and rebase this PR on top of master :)

[Voxelot]

It doesn't make sense to pollute the base fuel core image with extra utilities that aren't necessary. I.e. the primary fuel-core container should only contain the minimal amount of binaries to get the service running. Extra tools and CLIs could be done via side-cars or new dockerfiles that use this one as a base, as not everyone needs or wants this in every fuel-core container.