feat(core): make sentry optional

[Grvzard]

This may introduce a breaking change for users who have sentry in their production environment.
To make this PR work, #396 has to be merged first.

[Grvzard]

I just checked the commit ab1b717.
There is an oversight causing it to fail to compile in release mode:

pingora/pingora-core/src/server/mod.rs

Lines 121 to 122 in ab1b717

	#[cfg(not(debug_assertions))]
	sentry::capture_error(&e);

should be

#[cfg(all(not(debug_assertions), feature = "sentry"))]
sentry::capture_error(&e);

You can take a look at my commit for other places that need changes.

[eaufavor]

I believe that the change is fully merged into main now. Thanks