fix(gengapic): remove encoded quotes in query params

[noahdietz]

Removes all quotation marks from protojson encoded well known types that are encoded as strings. Lazily use strings.ReplaceAll to make it easier when the WKT doesn't necessarily have quotations included.

Showcase integration still works (some other languages do not encode quotations), and I tested locally with another API's samples.

Fixes #1363

[noahdietz]

cc: @Charlesleonius

[Charlesleonius]

What if there are valid quotes within the marshaled data?

[noahdietz]

Some quick testing of different WKT encodings: https://go.dev/play/p/kTiZbZRDd37

Number specific wrapper types e.g. DoubleValue will be encoded as the raw number, not a string, whereas BytesValue, for example, will be a quoted string. A ListValue or Value of any of the string-encoded wrapper types will also involve quotes but such a value isn't typically used in the query params...updated the solution to handle just the known string encoded types

[noahdietz]

What if there are valid quotes within the marshaled data?

Yeah I've switched back to that more targeted solution to avoid replacing quotes in StringValue fields.