Add extra checks before querying gl calls for MSAA.

[biagas]

Prevents potential crash on startup.
@markcmiller86 had the initial idea of testing if OGL window was current before making the gl call.
I had the idea of adding a call to MakeCurrent.
These weren't quite sufficient, codex added the rest and cleaned up the logic.

Description

Resolves #20920.

Type of change

• Bug fix~~
• New feature~~
• Documentation update~~
• Other~~

How Has This Been Tested?

Tested with no config files.
Tested with Config files with no rendering defaults changed.
Tested with config files with SR mode set to always
Tested with config file with antialiasing mode set to MSAA. (this no longer causes the crash, but antialising does not remain set to MSAA but rather, antialiasing gets turned off.)

On my Windows machine where MSAA should be available, it remains available in all these scenarios.

Reminders:

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Checklist:

• I have commented my code where applicable.~~
• I have updated the release notes.~~
• I have made corresponding changes to the documentation.~~
• I have added debugging support to my changes.~~
• I have added tests that prove my fix is effective or that my feature works.~~
• I have confirmed new and existing unit tests pass locally with my changes.~~
• I have added new baselines for any new tests to the repo.~~
• I have NOT made any changes to protocol or public interfaces in an RC branch.~~

[cyrush]

Looks good to me!

Are there other potentially other startup context race condition params?

[biagas]

Are there other potentially other startup context race condition params?

It's a possibility, of course, but I think at least for querying the MSAA availablity, I think we are covered.
On my Windows machine, when config file has SR set to always, first time MSAAAvailable is called, we call MakeCurrent, but it doesn't actually make the window current, so we return false.
The second time it is called, the window is current and other checks succeed, so we query GL_MAX_SAMPLES successfully.

With no config files (or config files with no rendering atts changed from default), when MSAAAvailable is called (opening rendering atts window or creating a plot), we call Make Current and that succeeds, then the query of GL_MAX_SAMPLES also succeeds.

[biagas]

Per concerns discussed in the bug ticket between Mark and myself, going to hold off on this until after the 3.5.0 release so we have more time to explore possible gotchas with this approach.
For 3.5 I will create a new PR that disables MMSA for now.