Add missing ops to exec module

[jarredholman]

It changes the following:

• Add support for executing ConditionalOp
• Add support for executing continue statements (it is missing label support like break)
• Remove the "match anything" branches where they weren't necessary.

[codecov]

Codecov Report

Merging #635 into master will increase coverage by 0.13%.
The diff coverage is 57.14%.

@@            Coverage Diff             @@
##           master     #635      +/-   ##
==========================================
+ Coverage   72.50%   72.64%   +0.13%     
==========================================
  Files         179      179              
  Lines       13376    13411      +35     
==========================================
+ Hits         9698     9742      +44     
+ Misses       3678     3669       -9     

Impacted Files	Coverage Δ
boa/src/exec/block/mod.rs	61.11% <0.00%> (-7.64%)	⬇️
boa/src/exec/statement_list.rs	61.11% <0.00%> (-7.64%)	⬇️
boa/src/exec/switch/mod.rs	62.96% <0.00%> (-5.04%)	⬇️
boa/src/exec/iteration/mod.rs	60.31% <25.00%> (-1.51%)	⬇️
boa/src/exec/break_node/mod.rs	100.00% <100.00%> (ø)
boa/src/exec/conditional/mod.rs	90.00% <100.00%> (+6.66%)	⬆️
boa/src/exec/iteration/tests.rs	100.00% <100.00%> (ø)
boa/src/exec/mod.rs	70.73% <100.00%> (+0.97%)	⬆️
boa/src/exec/tests.rs	100.00% <100.00%> (ø)
... and 4 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 14d7791...bd54a38. Read the comment docs.

[Razican]

Hi! I missed this PR, and #645 implemented part of it (the undefined part). Could you rebase?

[jarredholman]

rebased. Hopefully it is straightforward?
I implemented them the same way as If and Break

[Razican]

This looks good to me!