Make spelling of "initialize" consistent

[0xdaryl]

Of all uses of the word "initialize" (and its variants) in the compiler codebase (identifiers, comments, etc.), 2.4% of them use the British spelling "initialise". Change these to match the other 97.6% that spell it as "initialize".

This will make searching easier as one does not have to check for alternate spellings (yes, I'm grumpy because I was fooled by one of these recently).

This should generally be a straightforward change (only 26 uses in the compiler), however, please be careful with initialiseAOTRelocationHeader and initialiseRelocation as they will require downstream OpenJ9 changes too. One way of staging this would be to rename in OMR, create "initialise" versions in OMR that simply redirect to the "initialize" versions, merge your PR, make and merge the corresponding change in OpenJ9, and then remove the "initialise" versions in OMR.

This issue only covers the compiler codebase. There are other inconsistent uses throughout the rest of OMR that could/should be fixed up as well but are not tracked by this issue.