[oss][fboss] Introduce FBOSS github pull request template

[joseph5wu]

Pre-submission checklist

• I've ran the linters locally and fixed lint errors related to the files I modified in this PR. You can install the linters by running pip install -r requirements-dev.txt && pre-commit install
• pre-commit run

Summary

This PR will introduce a new FBOSS github pull request template which shows the pre-submission checklist, and the two basic sessions that Meta internal diff format: Summary and Test Plan

I also integrated pre-commit in this diff to allow clang formatting which is using the .clang-format in our fboss directory.
Once a user run pre-commit run once, it will automatically create a hook and will trigger the pre-commit automatically every time when they run git commit.

TODO: In the future, I'll introduce clang-linter in the pre-commit so users can correct any linter error before commit

Test Plan

Unfortunately, I can't verify whether my .github/pull_request_template.md works in this diff when I was composing my PR description, because it only works in the default branch and my PR has to use a local branch.

But I did verify my pre-commit work by manually messed up with one file to violate the clang-format rule.
You can see when I try to amend my commit, now the file was modified to the right format

[root@2ce8c3df3a07 fboss]# git commit --amend
clang-format.............................................................Failed
- hook id: clang-format
- files were modified by this hook

Formatting [1/1] fboss/agent/state/tests/InterfaceTests.cpp

[root@2ce8c3df3a07 fboss]# git status
On branch fboss_pull_request_template
Changes to be committed:
  (use "git restore --staged <file>..." to unstage)
        modified:   fboss/agent/state/tests/InterfaceTests.cpp

Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git restore <file>..." to discard changes in working directory)
        modified:   fboss/agent/state/tests/InterfaceTests.cpp

[root@2ce8c3df3a07 fboss]# git diff
diff --git a/fboss/agent/state/tests/InterfaceTests.cpp b/fboss/agent/state/tests/InterfaceTests.cpp
index fc8685394d..f577b28dcc 100644
--- a/fboss/agent/state/tests/InterfaceTests.cpp
+++ b/fboss/agent/state/tests/InterfaceTests.cpp
@@ -801,7 +801,8 @@ TEST(Interface, getRemoteInterfacesBySwitchId) {

   remoteInterfaces->addNode(
       rif,
-      HwSwitchMatcher(std::unordered_set<SwitchID>(
+      HwSwitchMatcher(
+          std::unordered_set<SwitchID>(
               {static_cast<SwitchID>(static_cast<uint16_t>(remoteSwitchId))})));

   EXPECT_EQ(stateV2->getInterfaces(SwitchID(remoteSwitchId))->size(), 1);

[meta-codesync]

@joseph5wu has imported this pull request. If you are a Meta employee, you can view this in D85806947.

[meta-codesync]

@joseph5wu merged this pull request in 669b74a.