chore(release) 2.8.1 post-release

[kikito]

Steps required after the release of 2.8.1:

• Bumping Rockspec and Meta versions
• Changing rockspec protocol from git to http (see sister PR chore(rockspec) replace git protocol by https #8672 which modifies the release/2.8.x rockspec)
• Manual update of the changelog to include 2.8.1 changes.

[Murphy-hub]

Another solution is to upgrade lualocks to version 3.8.0

[kikito]

Double-checking that I didn't miss anything:

Diff between 2.8.0 (already in master) and the current release/2.8.x: 2.8.0...release/2.8.x

Going over every single commit on that list, making sure that it is already merged into master, or on this pr, or is not needed (merge commits):

• chore(rockspec) bump lua-resty-healthcheck 1.5.1 -> master already has it at 1.5.1
• chore(CHANGELOG) unreleased section and healthcheck bump -> master already has an unreleased section in the changelog, healthcheck bump included in changelog for 2.8.1
• fix(runloop) reschedule rebuild timers after running them -> merged into master by fix(runloop) reschedule rebuild timers after running them #8567
• chore(CHANGELOG) timer rescheduling fix changelog entry -> included by the changelog change on this PR
• chore(requirements) bump OpenSSL to 1.1.1n -> master already requires 1.1.1o
• docs(CHANGELOG) dependencies section updated -> included by the changelog change on this PR
• Merge pull request fix(runloop) reschedule rebuild timers after running them #8634 from Kong/fix/runloop_timer_rescheduling_28x and Merge pull request chore(requirements) bump OpenSSL to 1.1.1n #8635 from Kong/chore/bump_openssl_111n_28x -> merge commits that brought the previous 4 changes from master to 2.8.x, they bring no additional commits/info besides that
• perf(clustering) conditional rebuilding of router, plugins iterator a… was included in master by perf(clustering) conditional rebuilding of router, plugins iterator and balancer on dp #8519, this was a cherry-pick for the 2.8.x branch
• Merge pull request perf(clustering) conditional rebuilding of router, plugins iterator and balancer on dp (2.8) #8639 from Kong/perf/dp-hashes merge commit for previous cherry-pick, no action needed.
• fix(env) localize environ pointer merged into master by fix(env) localize environ pointer and early return on nil #8581
• chore(deps) bump resty.openssl from 0.8.6 to 0.8.7 already overriden by master, which is in 0.8.8
• docs(changelog) add 2.8.1 changes being included on this PR already
• docs(kong-admin-api.yml) update Admin API definition for 2.8.1 Not needed for 3.0.0 release, it's done as part of the release script
• docs(api) document header regex in autodocs admin api (https://github.com/Kong/kong/pull/8572[)](https://github.com/Kong/kong/commit/bca5b02af85b1b6d82953cbbc26a3269ed499ab4) already in master
• release: 2.8.1 included on this PR
• chore(scripts) add missing update_docker function was a backport from master
• chore(rockspec) replace git protocol by https done on this PR
• [chore(deps) bump openssl from 1.1.1n to 1.1.1o] (47de055) master already at 1.1.1p
• Merge pull request Bump openssl 1.1.1o (backport 2.8) #8809 from Kong/chore/bump-openssl-1.1.1o merge commit for 1.1.1p openssl, no need to include anything