Improve shell identifier on case-insensitive system

[JamzumSum]

Use case-insensitive regex to remove .exe extension.

See: #22036 (comment)

[karrtikr]

Thanks for the PR, can you please add a testcase for this?

[karrtikr]

For eg. you can add one here:

vscode-python/src/test/common/terminals/shellDetectors/shellDetectors.unit.test.ts

Line 32 in 8e09243

shellPathsAndIdentification.set('c:\\windows\\system32\\bash.exe', TerminalShellType.bash);

[JamzumSum]

For eg. you can add one here:

vscode-python/src/test/common/terminals/shellDetectors/shellDetectors.unit.test.ts

Line 32 in 8e09243

shellPathsAndIdentification.set('c:\\windows\\system32\\bash.exe', TerminalShellType.bash);

Sure. A case-sensitive input is added in the test case now.

[JamzumSum]

@microsoft-github-policy-service agree

[karrtikr]

LGTM