Backport 0.14.x: feat(http1): support configurable max_headers

[IvanGoncharov]

Backport #3523 to 0.14.x.

Context: At my work, we can't update to 1.x, but we need this change to fix the customer's issue. I backported #3523 and tried to resolve all conflicts. Tests are passing, but I'm not sure about a few places. I will mark this place with comments.