Make LSP report new() as _init & fixes docstrings on multiline functions [3.x]

[Razoric480]

3.x cousin to #53092 , along with an additional fix that is 3.x specific where functions that are on multiple lines, I.E.:

# doc string
func multiline_func(
	parameter_a: int
) -> void:

do not detect the doc string.

Related to #51617, partial fixes.

[akien-mga]

Thanks!

[akien-mga]

Cherry-picked for 3.3.4.