Update minimal supported Bazel version to 6.3.0

[liucijus]

Bump supported Bazel to 6.3.0

We need to bump Bazel version to ease dealing with backwards incompatible changes from 6 and future version.

Motivation:

• Update dependency tracking patterns, which got affected with the release of 6
• Prepare for bzlmod changes, in case someone volunteers to work on it