Polish copyright headers and other org changes

[simonbasle]

This PR will introduce several commits updating the codebase to be in line with
past organizational changes, like VMware replacing Pivotal in copyright headers,
polishing of date ranges in same headers, pom org and developer list updates.

see reactor/reactor#682

[simonbasle]

how the copyright replacement was done:

1. search-and-replace on all files with regexp
   • from ([0-9]+)-[0-9]+ Pivotal Software Inc, All Rights Reserved (eg. 2017-2019)
   • to $1-2021 VMware Inc. or its affiliates, All Rights Reserved (eg. 2017-2021)
2. search-and-replace on all files with regexp
   • from ([0-9]+)-Present Pivotal Software Inc, All Rights Reserved (eg. 2017-Present)
   • to $1-2021 VMware Inc. or its affiliates, All Rights Reserved (eg. 2017-2021)

this was the first commit ☝️

second commit was to harmonize license header URL via a search-and-replace on all files with regexp
- ([ ]?[^ ])[ ]+https://www.apache.org (matching both # and * kind of comment blocks)
- $1 https://www.apache.org (harmonizing on 3 spaces: one for the comment block and 2 for indentation of the url, as in the ASF example)
- then rollback some of the files that are obviously not reactor's (the LICENSE file at root, some Gradle files...)

third commit was to find duplicate copyright headers via terminal:

for file in ./**/*; do if [ "$(grep -s -c "Copyright" "${file}")" -gt 1 ]; then echo "${file}"; fi; done

then the fourth commit was made to replace all the start dates with the same date (project inception, 2011):

• from 20[12][^1]-2021 VMware Inc (I made sure no 2021 start date was there)
• to 2011-2021 VMware Inc

[simonbasle]

the first two commits are the largest (hitting 800+ files) and the other commits are smaller. if you have trouble loading the large ones for review, here is the link to see smaller commits only: https://github.com/reactor/reactor-core/pull/2722/files/054f33f6954b88b459dc5f20a4ab47b85bc17b3a..1cd161835f3f7bc9ce27b3cdaa2268c8d89023d3

[simonbasle]

I'll merge this, forward-merge the change to main then follow-up with a similar change but in a single commit for files that have been added on main side (which should represent around 20 files)

[reactorbot]

@simonbasle this PR seems to have been merged on a maintenance branch, please ensure the change is merge-forwarded to intermediate maintenance branches and up to main 🙇