Update CloudWatch Logs MetricFilter handlers and template

[adam-daily]

This change makes several additions to bring this resource up to date and make it available for production. The resource passes contract tests and complies with the expectations outlined in: https://w.amazon.com/index.php/AWS21/Design/Uluru/HandlerContract

Testing:

(env) ➜  aws-logs-metricfilter git:(master) ✗ cfn-cli test
================================== test session starts ==================================
platform darwin -- Python 3.7.4, pytest-4.5.0, py-1.8.0, pluggy-0.12.0 -- /Users/adaily/Desktop/RPDK/aws-cloudformation-rpdk/env/bin/python3
cachedir: .pytest_cache
Test order randomisation NOT enabled. Enable with --random-order or --random-order-bucket=<bucket_type>
hypothesis profile 'default' -> database=DirectoryBasedExampleDatabase('/Users/adaily/Desktop/LogsResource/logs-fork/aws-logs-metricfilter/.hypothesis/examples')
rootdir: /Users/adaily/Desktop/LogsResource/logs-fork/aws-logs-metricfilter, inifile: /private/var/folders/65/6x_3qk7x4jz51hrxvj9f36pcrmvn8f/T/pytest_a07hibj5.ini
plugins: random-order-1.0.4, hypothesis-4.36.0, localserver-0.5.0, cov-2.7.1
collected 2 items

handler_misc.py::contract_check_asserts_work PASSED                               [ 50%]
handler_misc.py::contract_crud_exerciser ^@^@^@^@^@^@^@PASSED                                   [100%]

============================== 2 passed in 466.35 seconds ===============================

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[rjlohan]

The build is failing because of some changes to the CI in the backend. Look at the changes I made to the buildspec.yml and codebuild-ci.yaml in https://github.com/aws-cloudformation/aws-cloudformation-resource-providers-cloudfront/pull/5 and make similar changes in this repo to get build working again.

You also need to update the CI stack which one of us can show you.