Drop support for Bazel 5 & rules_apple 2

[luispadron]

This stops testing Bazel 5/rules_apple 2 in CI and bumps the support Bazel version in MODULE.bazel. It does not include any of the Bazel 5 related cleanup that is now possible. This is for an upcoming version 4.0.0.

Adds a table like the following to the read me:

Supported Bazel versions

Bazel release	Minimum supported rules version	Final supported rules version
6.*	2.0.0	current
5.*	1.0.0	3.2.2
4.*	1.0.0	1.0.0

Supported rules_apple versions

rules_apple release	Minimum supported rules version	Final supported rules version
3.*	3.*	current
2.*	2.*	3.2.2
1.*	1.0.0	3.2.2

[mattrobmattrob]

Awesome job!