Fix validation in the storage modal mount path

[DaoDaoNoCode]

JIRA: https://issues.redhat.com/browse/RHOAIENG-7680

Description

There is something wrong with the logic in the helper text and what error text we should show. I made some changes to that to correct the logic. Also, change the regex to allow a trailing / in the path.

Initial state:

Trailing slash:

Duplicate path:

Empty input:

Invalid value (contains number):

Invalid value (slash is not the trailing slash):

How Has This Been Tested?

1. Create a cluster storage
2. Attach it to a workbench
3. Input in the mouth path field, check if it's allowing a trailing slash
4. Check all the error states as listed above

Test Impact

Updated the cypress test to check the error cases.

Request review criteria:

Self checklist (all need to be checked):

• The developer has manually tested the changes and verified that the changes work
• Testing instructions have been added in the PR body (for PRs involving changes that are not immediately obvious).
• The developer has added tests or explained why testing cannot be added (unit or cypress tests for related changes)

If you have UI changes:

• Included any necessary screenshots or gifs if it was a UI change.
• Included tags to the UX team if it was a UI/UX change.

After the PR is posted & before it merges:

• The developer has tested their solution on a cluster by using the image produced by the PR to main

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[DaoDaoNoCode]

@andrewballantyne The bug you mentioned in #3231 (review) is not because of the connection path starts with a preexisting connection path, it's because you have a number 2 in your path, which is not allowed. The code had wrong logic of checking the error cases so it was showing an incorrect error message. The logic is fixed now in this PR.

[andrewballantyne]

That logic is likely wrong fwiw -- but I suppose this PR doesn't have to deal with that

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

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Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3236   +/-   ##
=======================================
  Coverage        ?   85.48%           
=======================================
  Files           ?     1280           
  Lines           ?    28228           
  Branches        ?     7557           
=======================================
  Hits            ?    24132           
  Misses          ?     4096           
  Partials        ?        0           

Files with missing lines	Coverage Δ
frontend/src/pages/projects/pvc/MountPathField.tsx	100.00% <100.00%> (ø)

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