fix: Validate intersection with multiple unions

[connor-g-swyftx]

This fixes a bug in validation of intersections with multiple unions. If the intersection includes at least three unions, only the first schema per union is accepted. One of the unions must have an overlapping required property to hit this bug.

I have written a failing test in f4531619fa75064cd980fe4d5f6c1654da4c3186, and fixed it in f5f5fdb3ffc9630ec245f1e5b62b472b0377d0e0.

There has been similar work in the past on intersection validation in https://github.com/lukeautry/tsoa/pull/888.

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Test plan

I've written parameterized tests to cover all valid schema combinations, and parameterized tests for invalid inputs covering invalid dataypes, missing required properties, and excess properties.

[WoH]

Can you slap a return type onto buildContext (any/unknown is fine) to get the CI result? LGTM, but I want the CI to confirm

[connor-g-swyftx]

@WoH done, thanks