test: fix coverage reports from codecov

[armano2]

Bash uploader used for sending coverage reports to codecov currently is broken for azure pipelines.

This fixes missing pr in query sent to codecov by providing it as parameter

Codecov bash script https://codecov.io/bash

-P pr
Specify the pull request number

Pipelines docs https://docs.microsoft.com/en-us/azure/devops/pipelines/build/variables?view=azure-devops&tabs=yaml

System.PullRequest.PullRequestNumber
The number of the pull request that caused this build. This variable is populated for pull requests from GitHub which have a different pull request ID and pull request number.

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Codecov link

https://codecov.io/gh/typescript-eslint/typescript-eslint/pull/1528/commits

Pipelines action

https://dev.azure.com/typescript-eslint/TypeScript%20ESLint/_build/results?buildId=3139&view=logs&jobId=18ce2c0c-8e5f-561b-2a1a-c5027ed6632f&j=18ce2c0c-8e5f-561b-2a1a-c5027ed6632f&t=477fddef-3d25-5c61-8626-53dac583e4f5

pr=1528

query: branch=merge&commit=23be3107029912cf459f3b3cb9de1bdb768d7a9b&build=20200126.2&build_url=https%3A%2F%2Fdev.azure.com%2Ftypescript-eslint%2FTypeScript%20ESLint%2F_build%2Fresults%3FbuildId%3D3139&name=&tag=&slug=typescript-eslint%2Ftypescript-eslint&service=azure_pipelines&flags=&pr=1528&job=3139&project=TypeScriptESLint&server_uri=https://dev.azure.com/typescript-eslint/

codecov/codecov-bash#189