Update Envoy to 12b3d2c2ffa582507e5d6dd34632b2b990f1b195

[oschaaf]

Notable changes in this Update:

• Changes related to header construction
• CI moves from clang-9 to clang-10
• Changes related to satisfy the new clang-tidy version:
  • Fix superfluous initializers in the rate limiter code.
  • Suppress modernize-avoid-bind to get sequencer_test.cc to pass checks.
    (clang-tidy's auto generated suggested fix fails to build)
• Move to use typed configs in AddFilter() in the server filter tests.
  This avoids asserts being triggered by the integration test framework
  as deprecated fields for which support was dropped get generated
  otherwise.
• Drop the coverage threshold by 0.1%

Hopefully addresses #362 by producing more reliable and accurate
coverage reports.

Signed-off-by: Otto van der Schaaf oschaaf@we-amp.com

---

prerequisite before merge

• Analyse why coverage dropped 0.1%
• Check api: deprecate hosts in Cluster. envoy#9663 to analyse
  impact on NH, if any. Possibly we need to move away some code
  from deprecated cluster field usage. (filed Move away from using hidden_envoy_deprecated_hosts #377)

[oschaaf]

The coverage threshold had to be lowered because of small changes, probably related to clang-10.

For example, compare the new factories impl coverage with the latest from master.
Both count these as missing coverage, but only the new version reports that the default switch label isn't hit:

(new)
     102           0 :   default:
     103           0 :     NOT_REACHED_GCOVR_EXCL_LINE;

(old)
     102          75 :   default:
     103           0 :     NOT_REACHED_GCOVR_EXCL_LINE;

I think that makes sense, and that the new version is more accurate. So lowering the coverage threshold seems
the right thing to do.