ROX-31485: Add build and push image to repo

[mtodor]

Description

This PR adds build and push image to quay.io.

• we build and push images for for architectures (amd64, arm64, ppc64le, and s390x)
• README is updated to reflect changes
• Dockerfile is adjusted to support cross-platform compiling
• Makefile VERSION is changed to take git commit

Validation

• checked pushed image: https://quay.io/repository/stackrox-io/mcp?tab=tags
• pull and run image locally

[codecov-commenter]

❌ 2 Tests Failed:

Tests completed	Failed	Passed	Skipped
158	2	156	0

View the top 2 failed test(s) by shortest run time

github.com/stackrox/stackrox-mcp/internal/testutil::

Stack Traces | 0s run time

Build error

github.com/stackrox/stackrox-mcp/internal/toolsets/mock::

Stack Traces | 0s run time

Build error

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