Feat: Allow non conflicting path methods to merge

[dbryar]

There is an open TODO in the queue to allow non-conflicting methods to merge in to the same path, so I've completed it.

The code may not be entirely the neatest (its a little bit of a hack), but open to suggestions.

[dbryar]

This also includes my previous MR for deep merging security schemes

[Fimeo]

Hi, did you find any issue to not merge this PR ?

[jmaver-plume]

@robertmassaioli Can this be merge?

[mpuigdomenchSage]

any chance this could be merged ?

[jfrconley]

@robertmassaioli Would be great if we could merge this