Matrix room/alias accepted characters re-aligned - bugfix

[caronc]

Description:

Related issue (if applicable): n/a

Improved handling of Matrix room/alias naming; This PR takes over from #1437 to address issue reported through Discord.

Checklist

• The code change is tested and works locally.
• There is no commented out code in this PR.
• No lint errors (use tox -e lint and even tox -e format to autofix what it can)
• Test coverage added (use tox -e minimal)

Testing

Anyone can help test this source code as follows:

# Create a virtual environment to work in as follows:
python3 -m venv apprise

# Change into our new directory
cd apprise

# If you have cloned the branch and have tox available to you
# the following can also allow you to test:
tox -e apprise -- -t "Test Title" -b "Test Message" \
          "matrix://credentials"

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.65%. Comparing base (74d5ad2) to head (67a479a).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1442   +/-   ##
=======================================
  Coverage   99.65%   99.65%           
=======================================
  Files         174      174           
  Lines       22554    22561    +7     
  Branches     3587     3590    +3     
=======================================
+ Hits        22476    22483    +7     
  Misses         70       70           
  Partials        8        8           

Files with missing lines	Coverage Δ
apprise/plugins/matrix.py	100.00% <ø> (ø)

... and 1 file with indirect coverage changes

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