Add support for string based failure domains in makePool()

Summary: Add support to configure failure domains as a string in makePool

Reviewed By: ftimyo

Differential Revision: D34917780

fbshipit-source-id: 7b7e92530b21d7dde3171f287f40059bc7437842

remove "soft" from fail-open config names

Summary:
This is the first diff in series to incorporate hard tko into the "fail-open" functionality.

Previously fail-open would only consider soft tkos, i.e. when a certain percent of the whole pool goes into soft tko, we fail-open (stop tko-ing the remaining machines).

After the task is done (a few more diffs) we will count both soft and hard tkos to fail-open.

This diff does not hold functional changes - just renaming the configs and variables to get rid of mentioning only "soft" tko - to avoid confusion in the future.
BONUS: fix the test `test_fail_open` that's been [flaky](https://www.internalfb.com/intern/test/844424947507269?ref_report_id=0) since forever.

Reviewed By: stuclar, tang-jianfeng

Differential Revision: D34698574

fbshipit-source-id: 8e9570313dbee3f885cb96bf4f623fca8a23e314

docs: add GH button in support of Ukraine (facebook#389)

Summary:
Our mission at [Meta Open Source](https://opensource.facebook.com/) is to empower communities through open source, and we believe that it means building a welcoming and safe environment for all. As a part of this work, we are adding this banner in support for Ukraine during this crisis.

Pull Request resolved: facebook#389

Reviewed By: disylh

Differential Revision: D34630826

Pulled By: dmitryvinn-fb

fbshipit-source-id: dbced0824e23153598ab4212d4c12b7806c6800c

Fix flaky tests due to startup time

Summary:
Many tests seem to be failing because Memcache after restart will be connected,
but will not be ready to process traffic - therefore commands like `stats` will
return nothing and crash the test.

Fix this by sending a version ping after connect, and keep retrying until
Memcache process responds, or we hit max retries.

Also update some of the test logic to have better error messages if reading
stats fails, instead of a vague exception trace about `NoneType` (see test
plan).

NOTE: Not really sure what caused startup time to regress. Some of the failed
test tasks are from many weeks ago, so it's hard to trace back a particular
root cause diff.

Reviewed By: aeolyus

Differential Revision: D34123351

fbshipit-source-id: 668f13069f50bc34f981295ee70dfb5c71036943

Fix flaky tests due to startup time

Summary:
Many tests seem to be failing because Memcache after restart will be connected,
but will not be ready to process traffic - therefore commands like `stats` will
return nothing and crash the test.

Fix this by sending a version ping after connect, and keep retrying until
Memcache process responds, or we hit max retries.

Also update some of the test logic to have better error messages if reading
stats fails, instead of a vague exception trace about `NoneType` (see test
plan).

NOTE: Not really sure what caused startup time to regress. Some of the failed
test tasks are from many weeks ago, so it's hard to trace back a particular
root cause diff.

Reviewed By: aeolyus

Differential Revision: D34123351

fbshipit-source-id: 668f13069f50bc34f981295ee70dfb5c71036943

Fix flaky tests due to startup time

Summary:
Many tests seem to be failing because Memcache after restart will be connected,
but will not be ready to process traffic - therefore commands like `stats` will
return nothing and crash the test.

Fix this by sending a version ping after connect, and keep retrying until
Memcache process responds, or we hit max retries.

Also update some of the test logic to have better error messages if reading
stats fails, instead of a vague exception trace about `NoneType` (see test
plan).

NOTE: Not really sure what caused startup time to regress. Some of the failed
test tasks are from many weeks ago, so it's hard to trace back a particular
root cause diff.

Reviewed By: aeolyus

Differential Revision: D34123351

fbshipit-source-id: 668f13069f50bc34f981295ee70dfb5c71036943

AxonLogRoute tests

Summary:
As title, use mocked dead server to simulate fail delete, and invoke axonlog spool.

In order to get tw task id from SR in test, update mock SMC in TargetHooks to populate tw_task_id.

Reviewed By: stuclar

Differential Revision: D32395294

fbshipit-source-id: f90cad524f044b5c1c7aafe184eeb9751413556e

Expose IO thread pool in McRouter instance

Summary: Expose IO thread pool in McRouter instance

Reviewed By: mshatalov

Differential Revision: D33661185

fbshipit-source-id: ab3d819440e1e9269227e046c517ffa953f643fd

Update license headers for Meta

Summary: As title

Reviewed By: zertosh, Happytreat

Differential Revision: D33646066

fbshipit-source-id: 9e5961a9ce21ea4dbc2bc3df7febca70e6d955ac

logging: fix tsan error

Summary:
See discussion on:
https://fb.workplace.com/groups/threadsanitizer/posts/618585969412291

Reviewed By: Skory

Differential Revision: D33458874

fbshipit-source-id: 47829a71c66c2f254796ad59efa1f58c94287412