refactor(parse): Simplify message filtering and processing logic parseResult

[jeet-dhandha]

This pull request includes changes to the parseResults function in the packages/pglite/src/parse.ts file. The main goal of these changes is to improve the readability and maintainability of the code by using a Set for valid message types and replacing conditional statements with a switch statement.

Code readability and maintainability improvements:

• Introduced a Set named VALID_MESSAGE_TYPES to store valid message types and used it in the filter method.
• Replaced multiple if-else statements with a switch statement to handle different message types more clearly. [1] [2] [3]

[samwillis]

This is a great spot, thanks @jeet-dhandha

I made a couple of small tweaks and added a changeset. Merging now 🥳

[copiltembel]

Nit-pick: in the worst case scenario, we're running twice over the same set: once to filter and then to process the messages. We can do both in a single run and still maintain good readability by having a default clause on the switch in which we log or gather the unsupported message types.