fix: update Rust version in debug Dockerfiles and fix docs

[whiz-Tuhin]

Description

This PR fixes build failures when using BUILD_CONFIG=debug by
updating outdated Rust versions in debug Dockerfiles and
correcting documentation references.

Changes made:

• Updated 4 Dockerfile.debug files from Rust 1.81 to Rust
  1.86-bullseye to resolve dependency compatibility issues
• Fixed documentation to use correct make docker-build BUILD_CONFIG=debug syntax instead of non-existent
  docker-build-debug target

Files affected:

• control-planes/mgmt_api/Dockerfile.debug
• control-planes/kubernetes_provider/Dockerfile.debug
• sources/kubernetes/kubernetes-reactivator/Dockerfile.debug
• sources/kubernetes/kubernetes-proxy/Dockerfile.debug
• Documentation files in /docs/ and /.github/instructions/

Type of change

• This pull request fixes a bug in Drasi and has an associated issue
  issue (BUILD_CONFIG=debug fails: Several Dockerfile.debug files pinned to incompatible Rust 1.81 #316).

Fixes: #316

[whiz-Tuhin]

Hi @amansinghoriginal, I've been working on resolving issue #308, but encountered some build errors during the process. I've created this PR and a related issue to address the issues.
Could you take a look at the PR whenever convenient ?

[amansinghoriginal]

@whiz-Tuhin Thanks for this contribution. LGTM