Use jemalloc in Docker builds

[frenck]

Proposed change

We have been running into issues with releasing/building armhf and armv7 images (including nightly).

pip install runs into a MemoryError, the reason why it isn't completely clear. Something is eating up all available address space (thanks, @agners, for spotting/providing more details on that one).

This PR activates jemalloc as the memory allocator for the installation of requirements_all.txt. We use jemalloc in our environment to run hass itself already.

I've been able to reproduce the original issue locally; this change, for now, passes for all architectures. That said, the original behavior (even with jemalloc) is still visible in the maps, but at least is stays within limits for now.

ℹ️ Not tagging this for a patch release just yet, as I want to test a nightly first.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Deprecation (breaking change to happen in the future)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue:
• Link to documentation pull request:

Checklist

• The code change is tested and works locally.
• Local tests pass. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.
• I have followed the development checklist
• The code has been formatted using Black (black --fast homeassistant tests)
• Tests have been added to verify that the new code works.

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated for www.home-assistant.io

If the code communicates with devices, web services, or third-party tools:

• The manifest file has all fields filled out correctly.
  Updated and included derived files by running: python3 -m script.hassfest.
• New or updated dependencies have been added to requirements_all.txt.
  Updated by running python3 -m script.gen_requirements_all.
• For the updated dependencies - a link to the changelog, or at minimum a diff between library versions is added to the PR description.
• Untested files have been added to .coveragerc.

To help with the load of incoming pull requests:

• I have reviewed two other open pull requests in this repository.

[frenck]

pytest failure is unrelated. Non of the pytests are affected by this PR. Going to merge it in.