Remove binary scalar operator number selector caching

[saswatamcode]

This PR removes the number selector caching from the binary scalar operator, which caused wrong results if a scalar selects from storage.
This caching is now handled by the step invariant operator instead.

For example,

For expression: 10 + scalar(max(http_requests_total))

[*CancellableOperator]: [*scalarOperator] +:
├──[*CancellableOperator]: [*stepInvariantOperator]:
│  └──[*CancellableOperator]: [*numberLiteralSelector] 10
└──[*CancellableOperator]: [*functionOperator] scalar(max(http_requests_total)):
   └──[*CancellableOperator]: [*concurrencyOperator(buff=2)]:
      └──[*CancellableOperator]: [*aggregate] max by ([]):
         └──[*CancellableOperator]: [*coalesceOperator]:
            ├──[*concurrencyOperator(buff=2)]:
            │  └──[*CancellableOperator]: [*vectorSelector] {[__name__="http_requests_total"]} 0 mod 4
            ├──[*concurrencyOperator(buff=2)]:
            │  └──[*CancellableOperator]: [*vectorSelector] {[__name__="http_requests_total"]} 1 mod 4
            ├──[*concurrencyOperator(buff=2)]:
            │  └──[*CancellableOperator]: [*vectorSelector] {[__name__="http_requests_total"]} 2 mod 4
            └──[*concurrencyOperator(buff=2)]:
               └──[*CancellableOperator]: [*vectorSelector] {[__name__="http_requests_total"]} 3 mod 4

For expression: scalar(max(http_requests_total)) + 10

[*CancellableOperator]: [*scalarOperator] +:
├──[*CancellableOperator]: [*functionOperator] scalar(max(http_requests_total)):
│  └──[*CancellableOperator]: [*concurrencyOperator(buff=2)]:
│     └──[*CancellableOperator]: [*aggregate] max by ([]):
│        └──[*CancellableOperator]: [*coalesceOperator]:
│           ├──[*concurrencyOperator(buff=2)]:
│           │  └──[*CancellableOperator]: [*vectorSelector] {[__name__="http_requests_total"]} 0 mod 4
│           ├──[*concurrencyOperator(buff=2)]:
│           │  └──[*CancellableOperator]: [*vectorSelector] {[__name__="http_requests_total"]} 1 mod 4
│           ├──[*concurrencyOperator(buff=2)]:
│           │  └──[*CancellableOperator]: [*vectorSelector] {[__name__="http_requests_total"]} 2 mod 4
│           └──[*concurrencyOperator(buff=2)]:
│              └──[*CancellableOperator]: [*vectorSelector] {[__name__="http_requests_total"]} 3 mod 4
└──[*CancellableOperator]: [*stepInvariantOperator]:
   └──[*CancellableOperator]: [*numberLiteralSelector] 10

Fixes #87.

[fpetkovski]

Thanks for fixing this, lgtm 👍

[GiedriusS]

👍