Make all test cases in W3C trace-context test suite pass

[xiang17]

Fixed errors and failures (marked as "Fixed in this PR" below) in W3C Trace Context tests of #1219. (Tracking individual test case would be easier after merging PR #1243, which parses the test run result and identifies individual test case status.)

Note on key format

There is an inconsistency in Trace Context v1 between the expressions and the description in the note below.

Expressions:

key = lcalpha 0*255( lcalpha / DIGIT / "_" / "-"/ "*" / "/" )
key = ( lcalpha / DIGIT ) 0*240( lcalpha / DIGIT / "_" / "-"/ "*" / "/" ) "@" lcalpha 0*13( lcalpha / DIGIT / "_" / "-"/ "*" / "/" )
lcalpha    = %x61-7A ; a-z

Note:

Note: Identifiers MUST begin with a lowercase letter or a digit, and can only contain lowercase letters (a-z), digits (0-9), underscores (_), dashes (-), asterisks (*), and forward slashes (/).

I think the first expression has a bug and the key should start with ( lcalpha / DIGIT ) instead of lcalpha to be consistent with the note of Trace Context v1 and the next version of specification being developed in w3c/trace-context repository.

The same note has been added in code as inline comment (Ctrl+F for "inconsistency").

Note on vendor format

Trace Context v1 which has W3C Recommendation status differs from the next version of specification being developed in w3c/trace-context repository regarding the "tenant@vendor" rules, which are covered by the following two test cases in the python test code.

Here I implemented the rules in accordance with Trace Context v1 as following to pass the python test case.

test_tracestate_key_illegal_vendor_format: The trace state is in such format tenant@vendor. Neither tenant and vendor can be empty. There can be at most one @. Otherwise remove all other list-members even if they are valid (in other words, remove all trace states).
test_tracestate_key_length_limit: The key can be up to 256 characters. Vendor up to 14. Tenant up to 241. Otherwise remove all trace states.

Explanation on version number

Regarding the failing two cases on version number and generating new trace_id (test_traceparent_version_0x00 and test_traceparent_version_0xff), the feature was working until a bug was introduced in this change.

Summary of the failures in Netcoreapp 2.1

Errors:

• test_tracestate_duplicated_keys: Fixed in this PR.
• test_tracestate_key_illegal_characters: Fixed in this PR.
• test_tracestate_key_illegal_vendor_format: Fixed in this PR.
• test_tracestate_key_length_limit: Fixed in this PR.
• test_tracestate_member_count_limit: Fixed in this PR.
• test_tracestate_multiple_headers_different_keys: Fixed in this PR.
• test_tracestate_value_illegal_characters: Fixed in this PR.

Failures:

• test_traceparent_trace_flags_illegal_characters: See issue Make all test cases in W3C trace-context test suite pass #1219.
• test_traceparent_version_0x00: Fixed in this PR.
• test_traceparent_version_0xff: Fixed in this PR.
• test_tracestate_empty_header: Fixed in this PR.

Summary of the failures in Netcoreapp 3.1

Errors:

• test_tracestate_duplicated_keys: Fixed in this PR.
• test_tracestate_key_illegal_characters: Fixed in this PR.
• test_tracestate_key_illegal_vendor_format: Fixed in this PR.
• test_tracestate_key_length_limit: Fixed in this PR.
• test_tracestate_member_count_limit: Fixed in this PR.
• test_tracestate_multiple_headers_different_keys: Fixed in this PR.
• test_tracestate_value_illegal_characters: Fixed in this PR.

Failures:

• test_traceparent_parent_id_all_zero: See issue Make all test cases in W3C trace-context test suite pass #1219.
• test_traceparent_parent_id_illegal_characters: See issue Make all test cases in W3C trace-context test suite pass #1219.
• test_traceparent_trace_flags_illegal_characters: See issue Make all test cases in W3C trace-context test suite pass #1219.
• test_traceparent_version_0x00: Fixed in this PR.
• test_traceparent_version_0xff: Fixed in this PR.
• test_tracestate_empty_header: Fixed in this PR.

Summary of the failures in Netcoreapp 5.0

Errors:

• test_tracestate_key_illegal_vendor_format: Fixed in this PR.
• test_tracestate_key_length_limit: Fixed in this PR.

Failures:

• test_traceparent_parent_id_all_zero: See issue Make all test cases in W3C trace-context test suite pass #1219.
• test_traceparent_parent_id_illegal_characters: See issue Make all test cases in W3C trace-context test suite pass #1219.
• test_traceparent_trace_flags_illegal_characters: See issue Make all test cases in W3C trace-context test suite pass #1219.
• test_traceparent_version_0x00: Fixed in this PR.
• test_traceparent_version_0xff: Fixed in this PR.

[codecov]

Codecov Report

Merging #1668 (a25f323) into master (e24dccb) will increase coverage by 0.21%.
The diff coverage is 98.70%.

@@            Coverage Diff             @@
##           master    #1668      +/-   ##
==========================================
+ Coverage   81.90%   82.12%   +0.21%     
==========================================
  Files         245      245              
  Lines        6637     6706      +69     
==========================================
+ Hits         5436     5507      +71     
+ Misses       1201     1199       -2     

Impacted Files	Coverage Δ
....Api/Context/Propagation/TraceContextPropagator.cs	87.64% <98.70%> (+11.40%)	⬆️
...ZPages/Implementation/ZPagesExporterEventSource.cs	56.25% <0.00%> (-6.25%)	⬇️

[CodeBlanch]

LGTM