[Colocation][YSQL] Fix ADD PRIMARY KEY setting colocated when it was unset

[jaki]

Jira Link: [DB-384](https://yugabyte.atlassian.net/browse/DB-384)
ALTER TABLE ADD PRIMARY KEY or ALTER TABLE ADD CONSTRAINT ... PRIMARY KEY may fail with error message

ERROR:  cannot set colocated true on a non-colocated database

even when the user does nothing related to colocation. It happens when the table has any reloptions set (see SELECT reloptions FROM pg_class WHERE relname = 'mytabname'). Since pk is tied to the main table, adding a primary key is done by creating a new table (YBCloneRelationSetPrimaryKey). One part of it does

	} else if ((*mutable_rel)->rd_options) {
		const bool colocated = RelationGetColocated(*mutable_rel);
		create_stmt->options = lappend(create_stmt->options,
			makeDefElem("colocated", (Node *) makeInteger(colocated), -1));

meaning that, if any reloptions are set, the colocated reloptions is copied over. However, the colocated reloption could be unset while some other reloption, like fillfactor, was set, so this could end up explicitly setting colocated to the default value (true). There is a check later on that makes sure colocation is unset or false when operating on a noncolocated database (the default), so the error is thrown.

Repro:

-- in noncolocated database
CREATE TABLE t (i int) WITH (autovacuum_enabled = true);
ALTER TABLE t ADD PRIMARY KEY (i);

Issue #9129 could have reduced the scope of this bug.

Credits to Suranjan Kumar for the initial bug report and Ted Yu for tracing to the root cause.