[Lang] Add statementArray methods and switch over CUDA

[dmed256]

Description

• Adds statementArray to make code transformation cleaner and safer
• Moves logic for fetching inner statements to statement_t
• Moves logic for fetching and replacing exprNodes to statement_t

[codecov]

Codecov Report

Merging #404 into main will decrease coverage by 0.61%.
The diff coverage is 81.49%.

@@            Coverage Diff             @@
##             main     #404      +/-   ##
==========================================
- Coverage   77.11%   76.50%   -0.62%     
==========================================
  Files         239      238       -1     
  Lines       18392    18306      -86     
==========================================
- Hits        14183    14005     -178     
- Misses       4209     4301      +92     

Impacted Files	Coverage Δ
include/occa/lang/statement/statement.hpp	100.00% <ø> (ø)
src/core/kernel.cpp	89.67% <ø> (ø)
src/lang/builtins/attributes/barrier.cpp	21.05% <0.00%> (ø)
src/lang/builtins/attributes/globalPtr.cpp	26.66% <0.00%> (ø)
src/lang/builtins/attributes/implicitArg.cpp	30.76% <0.00%> (ø)
src/lang/type/function.cpp	38.59% <0.00%> (-11.41%)	⬇️
src/tools/sys.cpp	65.14% <0.00%> (-0.16%)	⬇️
src/lang/modes/serial.cpp	41.78% <16.07%> (-15.19%)	⬇️
src/lang/statement/elifStatement.cpp	45.16% <45.16%> (ø)
src/lang/variable.cpp	68.29% <64.28%> (-2.58%)	⬇️
... and 58 more

[dmed256]

Tested locally + on libP (Thank you @tcew!)