[SECENG-582] Make policy decisions locally

[sagar-connect]

Checklist

=========

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have checked for similar issues and haven't found anything relevant.
• This is not a security issue (which should be reported here: https://circleci.com/security/)
• I have read Contribution Guidelines.

Changes

=======

• imported circle-policy-agent to the project to use cpa for local policy evaluations
• Extended decide sub-command to also perform policy evaluations locally
• redeclared org-id flag in decide subcommand to make it optional flag
• added tests to verify changes
• minor flag help text update for org-id
• rename test.yaml to test.yml

Rationale

=========

The current implementation of decide subcommand performs policy decision using policy-service
This PR extends decide subcommand to perform policy evaluation locally using imported circle-policy-agent

Considerations

==============

• Extended the existing subcommand instead of creating a new subcommand, the local vs remote execution based on whether --policy flag is provided or not
• --policy flag can be used to provide either of a policy file or directory containing policy files

[codecov]

Codecov Report

Merging #740 (d6cd3b2) into master (897ebaf) will increase coverage by 0.21%.
The diff coverage is 70.00%.

@@            Coverage Diff             @@
##           master     #740      +/-   ##
==========================================
+ Coverage   31.59%   31.81%   +0.21%     
==========================================
  Files          44       44              
  Lines        5295     5322      +27     
==========================================
+ Hits         1673     1693      +20     
- Misses       3376     3379       +3     
- Partials      246      250       +4     

Impacted Files	Coverage Δ
cmd/policy/policy.go	79.29% <70.00%> (-0.71%)	⬇️

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