Remove `shared_requirements.txt`, update dependency checks and handling

[scbedd]

Currently, this SDK prevents accidental dependency on broken requirements by the following.

1. shared_requirements.txt
2. min/max dependencies installed and tested nightly

We do this to ensure that all of the sdk-for-python packages can be installed alongside each other and still work appropriately.

Unfortunately, due to lack of investment into the check, the shared_requirements.txt check has become overwhelmed by exceptions to the "one single shared req." It effectively controls new requirements, but that's about it.

Update this check:

• [ ] Remove override concept, the packages themselves specify our dependencies
• [ ] Still catch on new specifiers being added -- resolution is to add to dependencies.txt
• [ ] Calculate dependency web, throw if an incoming change causes an irreconcilable conflict.
• [ ] Replace shared_requirement.txt in favor of dependencies.txt which is still at the root of the repo, but only contains names of packages that we require from directly from our packages. EG: [azure-core, isodate ] etc.

[azure-sdk]

Label prediction was below confidence level 0.6 for Model:ServiceLabels: 'Azure.Core:0.557367,Storage:0.13002592,Azure.Identity:0.032166276'

[scbedd]

Completed the shared_requirement simplification. Need to add poetry deep validation.