🐛 revert making RequiredPullRequestReviews a pointer

[spencerschrock]

While the current approach works with the tiered scoring, it wont work for probes or if we remove tiers. Making the struct nil to signal that PRs aren't required hides some of the data we do have.

This is especially problematic for repo rules, where we can infer all settings by what we see or don't see.

What kind of change does this PR introduce?

bug fix, followup of #3499

• PR title follows the guidelines defined in our pull request documentation

What is the current behavior?

RequiredPullRequestReviews is a pointer

What is the new behavior (if this is a feature change)?**

RequiredPullRequestReviews is a struct again
there's a new field Required *bool to measure if the PRs are required

• Tests for the changes have been added (for bug fixes/features)

Which issue(s) this PR fixes

Special notes for your reviewer

The most important changes are in clients/githubrepo/branches.go:

1. For admin tokens, Required is assumed to be &false, unless we have data otherwise.
2. For non admin tokens, Required is left nil, unless we have data otherwise.
3. For repo rules, Required is assumed to be &false, unless we have data otherwise.

In tests anything that had a non-nil RequiredPullRequestReviews was saying PRs were required:

RequiredPullRequestReviews: &clients.PullRequestReviewRule{

Which is now represented by:

RequiredPullRequestReviews: clients.PullRequestReviewRule{
	Required:                     &trueVal,

similarly, anything which was:

RequiredPullRequestReviews: nil,

is now:

RequiredPullRequestReviews: clients.PullRequestReviewRule{
	Required: &falseVal,

Does this PR introduce a user-facing change?

For user-facing changes, please add a concise, human-readable release note to
the release-note

(In particular, describe what changes users might need to make in their
application as a result of this pull request.)

NONE

[spencerschrock]

@diogoteles08 as the person most familiar with the code, can you take a first look?

[codecov]

Codecov Report

Merging #3728 (fd2a139) into main (663e1a9) will decrease coverage by 9.48%.
The diff coverage is 78.18%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3728      +/-   ##
==========================================
- Coverage   76.04%   66.56%   -9.48%     
==========================================
  Files         214      214              
  Lines       14803    14797       -6     
==========================================
- Hits        11257     9850    -1407     
- Misses       2871     4383    +1512     
+ Partials      675      564     -111     

[diogoteles08]

PR looks great to me and follows what I was expecting as well.
I commented some minor inconsistencies and doubts.