Move physical expression planning to datafusion-physical-expr crate

[andygrove]

Which issue does this PR close?

Closes #2535

Rationale for this change

The main motivation was to not have SimplifyExpressions depend on the core datafusion crate so that we can move it to the new datafusion-optimizer crate

What changes are included in this PR?

Move the following items from core to datafusion-physical-expr:

• create_physical_expr
• ExecutionProps
• VarProvider
• ScalarFunctionExpr

Are there any user-facing changes?

Not too much since I added re-exports but this is still an API change.

[codecov-commenter]

Codecov Report

Merging #2682 (f3d5d71) into master (49e072a) will increase coverage by 0.00%.
The diff coverage is 86.22%.

@@           Coverage Diff           @@
##           master    #2682   +/-   ##
=======================================
  Coverage   84.63%   84.64%           
=======================================
  Files         267      269    +2     
  Lines       46867    46926   +59     
=======================================
+ Hits        39665    39719   +54     
- Misses       7202     7207    +5     

Impacted Files	Coverage Δ
datafusion/core/src/execution/context.rs	78.78% <ø> (-0.10%)	⬇️
...afusion/core/src/optimizer/simplify_expressions.rs	82.00% <ø> (ø)
datafusion/core/src/physical_optimizer/pruning.rs	93.77% <ø> (ø)
datafusion/core/src/physical_plan/mod.rs	88.00% <ø> (ø)
datafusion/core/src/physical_plan/planner.rs	77.51% <ø> (-1.82%)	⬇️
datafusion/physical-expr/src/from_slice.rs	100.00% <ø> (ø)
datafusion/physical-expr/src/functions.rs	94.19% <ø> (+28.57%)	⬆️
datafusion/physical-expr/src/type_coercion.rs	98.73% <ø> (ø)
datafusion/physical-expr/src/udf.rs	100.00% <ø> (ø)
datafusion/physical-expr/src/scalar_function.rs	65.62% <65.62%> (ø)
... and 9 more

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[alamb]

I obviously didn't review this entire PR in detail but I checked that the tests remained intact and everything else looks good. Thank you @andygrove I really like how the modularization is proceeding