Add ConflictingLocksError class (backport #6852) [release/4.7.x]

[mergify]

Taken from imodels-clients. So that they can surface this error properly to users and and those users can show some useful UI about who has their locks.

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This is an automatic backport of pull request #6852 done by Mergify.

[mergify]

Cherry-pick of 20cd3cd has failed:

On branch mergify/bp/release/4.7.x/pr-6852
Your branch is up to date with 'origin/release/4.7.x'.

You are currently cherry-picking commit 20cd3cdcca.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   common/api/core-backend.api.md
	modified:   common/api/core-common.api.md
	modified:   common/api/summary/core-backend.exports.csv
	modified:   common/api/summary/core-common.exports.csv
	new file:   common/changes/@itwin/core-backend/nick-conflictinglockserror_2024-06-17-17-47.json
	new file:   common/changes/@itwin/core-common/nick-conflictinglockserror_2024-06-17-17-47.json
	modified:   core/backend/src/BackendHubAccess.ts
	modified:   core/backend/src/IModelDb.ts
	modified:   core/backend/src/LocalHub.ts
	modified:   core/backend/src/ServerBasedLocks.ts
	modified:   core/backend/src/test/standalone/HubMock.test.ts
	modified:   core/backend/src/test/standalone/ServerBasedLocks.test.ts
	modified:   core/common/src/IModelError.ts

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   core/backend/src/test/standalone/IModelWrite.test.ts

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[mergify]

This pull request is now in conflicts. Could you fix it @mergify[bot]? 🙏
To fixup this pull request, you can check out it locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

[aruniverse]

@nick4598 @austeja-bentley we can re-open this if we need to