[E2E Test] Use isolated venv for test_on_demand_capacity_reservation to avoid affecting parallel tests

[hehe7318]

Description of changes

Previously, the test reinstalled pcluster CLI globally with a patched version, which could interfere with other tests running in parallel.

Now the patched CLI is installed into an isolated virtual environment in /tmp, leaving the system pcluster unchanged.

Tests

I ran test_on_demand_capacity_reservation with test_build_image with all OSs in parallel with below config, test result looks good.

{%- import 'common.jinja2' as common with context -%}
{{- common.OSS_COMMERCIAL_X86.append("rocky8") or "" -}}
{{- common.OSS_COMMERCIAL_X86.append("rocky9") or "" -}}
---
test-suites:
  capacity_reservations:
    test_on_demand_capacity_reservation.py::test_on_demand_capacity_reservation:
      dimensions:
        - regions: ["us-west-2"]
          instances: {{ common.INSTANCES_DEFAULT_X86 }}
          oss: [{{ OS_X86_3 }}]
  createami:
    test_createami.py::test_build_image:
      dimensions:
        - regions: ["usw2-az1"]
          instances: ["g4dn.2xlarge"]
          schedulers: [ "slurm" ]
          oss: {{ common.OSS_COMMERCIAL_X86 }}

Checklist

• Make sure you are pointing to the right branch.
• If you're creating a patch for a branch other than develop add the branch name as prefix in the PR title (e.g. [release-3.6]).
• Check all commits' messages are clear, describing what and why vs how.
• Make sure to have added unit tests or integration tests to cover the new/modified code.
• Check if documentation is impacted by this change.

Please review the guidelines for contributing and Pull Request Instructions.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.21%. Comparing base (6bd8e1d) to head (f4e9d80).
⚠️ Report is 1 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #7187   +/-   ##
========================================
  Coverage    90.21%   90.21%           
========================================
  Files          183      183           
  Lines        16566    16566           
========================================
  Hits         14945    14945           
  Misses        1621     1621           

Flag	Coverage Δ
unittests	90.21% <ø> (ø)

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