[Cosmos] Make eslint step mandatory and revert tslint

[HarshaNalluru]

PR #5429 temporarily enables tslint as part of the build step.
The changes from that PR have to be reverted once the eslint step is made mandatory.

/cc - @KarishmaGhiya @ramya-rao-a @willmtemple

[mikeharder]

@HarshaNalluru: Will tslint be removed from the cosmos dev dependencies when this issue is fixed? cosmos is the only package in our repo still using tslint.

[HarshaNalluru]

@mikeharder, yes.
We should probably make it a priority to fix the eslint errors in all the packages and make the step mandatory in the CI.

[deyaaeldeen]

I think this can be closed now since we no longer use tslint and eslint is run as part of the analyze step in CI.

[ramya-rao-a]

@deyaaeldeen This was needed to ensure we remove the tslint call in the build step after #10776 is done. We can close this if we include the above step in #10776 itself