[Phase 2][Post GA][YSQL] Allow changing the colocated table/database option after creation

[PatrLind]

Jira Link: [DB-369](https://yugabyte.atlassian.net/browse/DB-369)
At this time it is only possible to change the colocation option during database creation or during table creation in a already colocated database.

It would be very useful to be able to alter this on an already existing database or table as databases and data sets evolve over time.

Example how I imagine this could be changed by a user:

-- Change a table to be colocated regardless of the colocation status of the database
ALTER TABLE table_name WITH colocated = true;

-- Change all tables to be colocated unless opted out
ALTER DATABASE database_name WITH colocated = true;

[thinknirmal]

Duplicate of #4396

[snehalbhavsar916]

Me too had this problem, Initially I created database without colocated flag and thus it is by default false and my use case is that I have created database and imported 2-3 GB data in ysql, which resulted into increasing load on the database server. Then I tried altering the database and tables to set colocated =true, but it did not supported.

Also, if the architecture of yugabyte supports multiple tablets for large tables then it must be optimised to handle such cases.

[jaki]

keywords: pull, out, pull-out, opt-out, opt

This should be a dependency for #4396 because #4396 is this + automatic.

[mgrosso]

This feature would be important for an application I have attempted to proof-of-concept using with Yugabyte.

In my case, I would start with one database with colocation = 'true', create a number of schemas, and then colocate the subset of schemas that acquired enough data to merit that.

Less common, but probably needed, would be the ability to pull a table out of a colocated database or schema.

I would never need or want to un-colocate a schema or database once it was colocated, although some tables in them will need that obviously as requested in #4396