feat(bru-rmvar): add bru.rmVar(varType, key) command

[bpoulaindev]

Description

Referencing issue #2464

Add a new bru.rmVar() command that helps replicate pm.environment.unset()

The command is recognized in the UI and can edit content from envVariables, collectionVariables and also processEnvVars.
How to use : bru.rmVar([varType], [key])

Contribution Checklist:

• The pull request only addresses one issue or adds one feature.
• The pull request does not introduce any breaking changes
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• Create an issue and link to the pull request.

Note: Keeping the PR small and focused helps make it easier to review and merge. If you have multiple changes you want to make, please consider submitting them as separate pull requests.

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[bpoulaindev]

The commands #1714 are also interesting, and considering those are simple and necessary, while the PR is more than 3 months old is crazy

[martinsefcik]

If there are setVar/getVar and setEnvVar/getEnvVar methods why not to have rmVar and rmEnvVar?
In my eyes it is better as to introduce some weird and long varType strings which will be error prone because of typos during typing it.

[helloanoop]

Thank for taking time to work on this @bpoulaindev

Bruno now supports bru.deleteVar() which was implemented as a part of another PR
Closing this PR.