WIP: Simplified Agent Installer

[SoarinFerret]

The goal of this PR is to update the current agent installer (primarily for linux) to provide a simple command to copy/paste and then run on a remote server without having to copy an installer script around. If this is something of use to the devs, I would like to continue the work here to allow the same functionality on Windows. The macOS install command is pretty close to this already.

Here are the UI changes (provided in a separate PR on the amidaware/tacticalrmm-web repo)

[CLAassistant]

All committers have signed the CLA.

[codecov]

Codecov Report

Merging #1352 (e3cb957) into develop (0343ee4) will decrease coverage by 0.24%.
The diff coverage is 59.52%.

@@             Coverage Diff             @@
##           develop    #1352      +/-   ##
===========================================
- Coverage    82.34%   82.09%   -0.25%     
===========================================
  Files          114      114              
  Lines         7527     7558      +31     
===========================================
+ Hits          6198     6205       +7     
- Misses        1329     1353      +24     

Impacted Files	Coverage Δ
api/tacticalrmm/agents/urls.py	100.00% <ø> (ø)
api/tacticalrmm/agents/views.py	82.59% <50.00%> (-1.02%)	⬇️
api/tacticalrmm/agents/utils.py	56.89% <64.28%> (-22.60%)	⬇️

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[wh1te909]

Thanks for starting this, since the linux/mac agents are still in beta they are probably going to change a lot as I am just experimenting with stuff but my plan was to eventually get rid of the bash scripts for installing so this looks like a good start.

We're actually working on a contributing guide for both this and the web repo but it's not quite ready yet, so until then I'll just post a snippet from the contributing guide for python specifically, please incorporate this into your PR and lmk if have any questions on them. You can look through the code for examples of all of the below:

• All Django code submitted to the main tacticalrmm repo must have 100% unit test coverage.
• Lines that are not part of your change should not be edited (e.g. don't format
  unchanged lines, don't reorder existing imports)
• All python files must be formatted with black
• Type hints are required and will be enforced.
• With the exception of Django or DRF view functions, all functions must be fully type annotated and enforce named arguments (PEP 3102). Example:

# bad
def add_two_numbers(num1, num2):
    return num1 + num2

# good
def add_two_numbers(*, num1: int, num2: int) -> int:
    return num1 + num2

[SoarinFerret]

Thanks for the feedback, I'll do my best to incorporate those changes over the next couple of days!