Summary:
Adds YBA API to update PITR  schedule. The following changes have been made as part of this PR:

Support for updating PITR schedule RPC calls through yb-client.
API support from the Platform to update PITR schedule
Task framework support for updating PITR schedule

API path- PUT /api/v1/customers/f33e3c9b-75ab-4c30-80ad-cba85646ea39/universes/a383fd86-e512-42d8-b399-a761cc339560/pitr_config/3505219d-b819-4fee-9ef8-1e5a0c2f2260

Request body-
{
"retentionPeriodInSeconds": "345600" // mandatory
"intervalInSeconds":  "86400" // optional, if not provided the default is 86400 ie 1 day
}

Response-
{

"taskUUID": "76765f8a-afc8-4f76-b7df-4c1c4e6b7349"
}

Test Plan:
Tested manually in local env.
- Create YSQL and YCQl databases and corresponding snapshot schedules for them. Update these schedules (retention and interval updates were tested).
- Tested for negative cases against the pre validations done.

Reviewers: vkumar, #yba-api-review, sneelakantan

Reviewed By: vkumar, #yba-api-review, sneelakantan

Subscribers: yugaware

Differential Revision: https://phorge.dev.yugabyte.com/D40949