Support Bazel 6.0.0

[tpasternak]

1. Main Repository Target Label Prefixes.
   In Bazel 5 and older, the target labels were strigified to "//"-prefixed names. Since
   6.0.0, they are stringified to "@//"-prefixed names. Unfortunately, this does not apply
   to data coming from BEP. Targets references in BEP events payload are "//"-prefixed.
   For this reason we need to add "@" manually after retrieving data from BEP.

2. aspects.bzl: Retrieve runtime toolchain in the new way (Bazel 6.0.0)

3. cpp-project: Old GTest version is incompatible with Bazel 6.0.0, the
   new one required cpp version bump (--std=c++17)

4. e2e tests are now adapted to run across multiple Bazel versions (currently 5 and 6)

5. JdkResolver: JDK version was inferred from source version, which is not always true. That's
   why it is safer just to pass null.

[abrams27]

i feel that we can do it without bazel version - the bazel version is used only in 3 places:

• isWorkspaceTarget - we can just check does the id starts with // or @//
• similar for extracting the relative path

but then we could do it without passing BazelInfo around, what d u think about it?

[tpasternak]

i feel that we can do it without bazel version - the bazel version is used only in 3 places:

isWorkspaceTarget - we can just check does the id starts with // or @//
similar for extracting the relative path
but then we could do it without passing BazelInfo around, what d u think about it?

@abrams27 It would be good and less code indeed, but when I've been working on it, I considered // form as a legacy one, which we want to support only as long as we are going to support Bazel 5. Once we drop support 5, we may extract this code and use @// everywhere directly, without version checking