[BUG] Fuzz tests failure in profiling with labels

[morrisonlevi]

Describe the bug
This has triggered in CI and also for me locally:

Error: 
panicked at profiling/src/internal/profile/fuzz_tests.rs:365:13:
assertion `left == right` failed
  left: [Label { key: "\0ܔ", str: None, num: 0, num_unit: None }, Label { key: "\0\0", str: None, num: 0, num_unit: None }]
 right: [Label { key: "\0\0", str: Some(""), num: 1125900712148992, num_unit: Some("") }, Label { key: "\0ܔ", str: Some(""), num: 0, num_unit: Some("") }]

Error: 
panicked at profiling/src/internal/profile/fuzz_tests.rs:359:13:
assertion `left == right` failed
  left: [Label { key: "", str: None, num: 0, num_unit: None }, Label { key: "\0I", str: None, num: 0, num_unit: None }]
 right: [Label { key: "\0I", str: None, num: 0, num_unit: Some("") }, Label { key: "", str: Some(""), num: 0, num_unit: Some("") }]

To Reproduce
Steps to reproduce the behavior:

1. Check out a recent version of the repo.
2. Run cargo +nightly bolero test -p datadog-profiling internal::profile::fuzz_tests::test_fuzz_add_sample
3. Wait forever, it'll probably find it too

Expected behavior
Don't expect a fuzz test failure here.

Errors or warnings received
None, just a fuzz failure.

[morrisonlevi]

There are two issues here:

1. Some("") and None need to be treated as equivalent.
2. The order of the labels is not stable. The labels coming from the deserialized pprof may not be in insertion order because they are ordered by LabelId. These are strongly correlated to insertion order, but it's not the same.