Sc review build

[dragosgd]

Purpose

Finished review of the Build section in Smart Contracts according to the DOC-301 ticket

Changes

• removed mention of dalloc and replaced with a reference to bump_alloc, which is the latest recommended custom allocator
• added a note in the Use a custom allocator article mentioning to the user to be careful in the use of bump_alloc, with an example
• added references to cargo-concordium rust crate documentation
• replaced a reference to build-contract with a reference to setup-env, which is the main tutorial for installing dev tools
• added a reference in JSON parameters to a related guide on how to use them

Checklist

• My code follows the style of this project.
• The code compiles without warnings.
• I have performed a self-review of the changes.
• I have documented my code, in particular the intent of the
  hard-to-understand areas.
• (If necessary) I have updated the CHANGELOG.

CLA acceptance

By submitting the contribution I accept the terms and conditions of the
Contributor License Agreement v1.0

• link: https://developers.concordium.com/CLAs/Contributor-License-Agreement-v1.0.pdf

• I accept the above linked CLA.