Allow QuarkusTest to override base URL of REST client

[geoand]

Fixes: #10126

This PR provides the basic low level building blocks that are needed in order to support changing the baseURL in tests (just take a look at the changed test to see how it's meant to be used).
It can certainly be used by end users , but ideally it would also be used under the hood by higher level abstractions in the same way that QuarkusMock and InjectMock complement each other.

[geoand]

@kenfinnigan @asoldano what do you think about this? It obviously depends heavily on RESTEasy internals, but given how closely we collaborate, I don't think it will be a problem to have this as a first iteration - then if you agree we can look into providing proper hooks in the the RESTEasy codebase if you think we should.

[geoand]

@knutwannheden this solves #10126 that we talked about

[geoand]

PR is in draft and need a lot more testing

[kenfinnigan]

Is it not possible for test profile in application.properties to define the mock URL?

[geoand]

Sure, but this for changing the URL per test, without having to restart or rebuild anything. Same idea as we have with QuarkusMock

[kenfinnigan]

Why does the URL need to change per test? Wouldn't it be the same for all tests?

[geoand]

Because that limits you to only what the mock server can return, which I realize that in most cases would suffice, but limits some testing scenarios.

[knutwannheden]

I haven't tested it yet, but AFAICT #9933 would also be sufficient for my purposes.

[geoand]

Yeah, the test profiles are an excellent way to change properties.

[gsmet]

Lots of conflicts and didn't get any attention for a while. I will close it. We can still reopen it if we want to revisit.