Od/chore/casing for git provider

[sashaboi]

Description

Fixes https://github.com/codecov/engineering-team/issues/630 Replaces the correct cases for git providers. On my local setup all tests seem to pass, and I have modified quite a few as well, could we please run tests to see if everything is in order @nicholas-codecov ?

Notable Changes

Changes in the way provider.js handles things, please have a look

Legal Boilerplate

Look, I get it. The entity doing business as "Sentry" was incorporated in the State of Delaware in 2015 as Functional Software, Inc. In 2022 this entity acquired Codecov and as result Sentry is going to need some rights from me in order to utilize my contributions in this PR. So here's the deal: I retain all rights, title and interest in and to my contributions, and by keeping this boilerplate intact I confirm that Sentry can use, modify, copy, and redistribute my contributions, under Sentry's choice of terms.