[Serial] Add dynamic exclusive variable sizes

[noelchalmers]

Description

Adds Dynamic @exclusive sizes, closing #121.

When using @exclusives in Serial and OpenMP, OCCA's current behavior is to emulate thread-private variables by turning the @exclusive variable into a fixed-size array of length 256. The new behavior is as follows:

1. Default array length is now 1024 (to conform with GPU backends)
2. If @max_inner_dims is specified in the @outer block containing the @exclusive, the array length is set to @max_inner_dims.
3. If the @inner block sizes are known at compile time, the array length is set to this size.
4. If the size determined in 3 is larger than the size determined in 2, an error is thrown.

[codecov]

Codecov Report

Merging #625 (2227a5e) into development (50a8a9b) will decrease coverage by 0.23%.
The diff coverage is 0.00%.

Additional details and impacted files

@@               Coverage Diff               @@
##           development     #625      +/-   ##
===============================================
- Coverage        77.28%   77.04%   -0.24%     
===============================================
  Files              265      265              
  Lines            19570    19634      +64     
===============================================
+ Hits             15124    15127       +3     
- Misses            4446     4507      +61     

Impacted Files	Coverage Δ
src/occa/internal/lang/modes/serial.cpp	29.38% <0.00%> (-12.23%)	⬇️
src/occa/internal/utils/sys.cpp	76.88% <0.00%> (+0.10%)	⬆️
src/occa/internal/lang/specialMacros.cpp	60.26% <0.00%> (+0.66%)	⬆️