Fix environment variables and move envs.txt/event.json to fixed location

[catthehacker]

fix: move envs.txt & event.json to /tmp/workflow/

Since #635 envs.txt is not copying properly when running act in WSL2 (Linux <> Linux) (didn't tried it with Windows <> Linux scenario)
Moving it to fixed location resolves that as it doesn't need to move around since we have GITHUB_ENV
fix: environment variables sourcing from /etc/environment

[codecov]

Codecov Report

Merging #667 (2ba5489) into master (0f04942) will increase coverage by 0.50%.
The diff coverage is 51.96%.

@@            Coverage Diff             @@
##           master     #667      +/-   ##
==========================================
+ Coverage   49.27%   49.77%   +0.50%     
==========================================
  Files          23       23              
  Lines        2401     2469      +68     
==========================================
+ Hits         1183     1229      +46     
- Misses       1090     1104      +14     
- Partials      128      136       +8     

Impacted Files	Coverage Δ
pkg/container/docker_run.go	1.91% <0.00%> (-0.02%)	⬇️
pkg/runner/runner.go	76.47% <ø> (ø)
pkg/common/git.go	55.50% <20.00%> (-4.30%)	⬇️
pkg/model/workflow.go	30.71% <33.33%> (+5.00%)	⬆️
pkg/model/planner.go	34.56% <41.37%> (+1.48%)	⬆️
pkg/container/docker_pull.go	36.17% <64.70%> (+17.98%)	⬆️
pkg/runner/step_context.go	71.42% <84.61%> (+2.48%)	⬆️
pkg/runner/run_context.go	76.60% <93.33%> (+0.19%)	⬆️

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