ci: move scripts from '.github/gha' and '.github/travis' into '.github/scripts'

[umarcor]

Description

This PR moves scripts from .github/gha and .github/travis into .github/scripts. Scripts that use those resources are updated accordingly. BTW, the workflow YAML is slightly simplified.

Related Issue

Close #1755

Motivation and Context

Travis is non used anymore.

How Has This Been Tested?

CI is still all green.

Types of changes

• Bug fix (change which fixes an issue)
• New feature (change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My change requires a change to the documentation
• I have updated the documentation accordingly
• I have added tests to cover my changes
• All new and existing tests passed

Additional context

There are some remaining references to travis:

# grep -lr ./ -e "travis"
./abc/README.md
./libs/EXTERNAL/capnproto/README.md
./libs/EXTERNAL/libtatum/README.md

However, I assume that those are vendores dependencies, so they handle CI on their own.

[mithro]

I think the goal was to keep these scripts from depending on stuff under the .github directory.

[umarcor]

Yeah. That's what I thought. However, the common.sh is currently explicitly sourced. See

vtr-verilog-to-routing/.github/workflows/test.yml

Lines 37 to 59 in d3449e8

	Format:
	runs-on: ubuntu-18.04
	strategy:
	fail-fast: false
	matrix:
	include:
	- { name: 'C/C++', script: 'check-format.sh' }
	- { name: 'Python', script: 'check-format-py.sh' }
	- { name: 'Python Lint', script: 'pylint_check.py' }
	name: 'F: ${{ matrix.name }}'
	steps:
	- uses: actions/checkout@v2
	- run: ./.github/gha/install_dependencies.sh
	- uses: actions/setup-python@v2
	with:
	python-version: 3.6
	- run: pip install -r requirements.txt
	- name: Test
	run: |
	source .github/travis/common.sh
	./dev/${{ matrix.script }}

I tried to do minimal functional modifications in this PR. So, precisely, I preserved common to be sourced before/in check-format.sh and check-formar-py.sh, but I did not in pylint_check.py.

If you or any maintainer/developer can confirm that common.sh is not required in check-format.sh/check-formar-py.sh, I will update them.

Moreover, the git blame belongs to me. So, this is inherited from the previous .travis.yml file. There, the common script was source in all the jobs: 13a8c9f#diff-6ac3f79fc25d95cd1e3d51da53a4b21b939437392578a35ae8cd6d5366ca5485L243-L254