[Enhancement] consolidate build and assemble into single unified process

[tianleh]

Introduction

Inspired by #1812 (comment) and some follow up discussions with @dblock , I am summarizing the proposal to consolidate build and assemble into single unified process.

Current bundle artifact generation process consists of two steps.

The first step is build https://github.com/opensearch-project/opensearch-build/blob/main/build.sh It will take an input manifest as input and output a build manifest and related component artifacts. This is a screenshot of the output structure.

The second step is assemble https://github.com/opensearch-project/opensearch-build/blob/main/assemble.sh It will take the build manifest of previous build step and output the bundle manifest as well as the bundle artifact. This is a screenshot of the output structure.

Proposal

The proposal is to have a single process to perform the build and assemble work together. (e.g roll assemble into build) In this way, the intermediate output doesn't need to be persisted. (e.g build manifest) This will also simplify the current folder structures under the project root by removing both build and dist.

Call out

1. ARM build is cross platform.
2. Integ test needs the build manifest. https://github.com/opensearch-project/opensearch-build/blob/c96aff001188af8878465761302669dd464dbf0a/src/test_workflow/integ_test/integ_test_suite_opensearch_dashboards.py We may need to remove such dependency.