Jira Plugin: Refactor issue/epic search to reduce code duplication

Description

This PR makes the issue search route more flexible, allowing us to make more feature-rich help wanted tickets around searching for issues.

QA Test Steps

Smoke test for

  • searching for issues in attach modal

  • searching for epics in filter fields of subscribe modal

Mana

None

Assignee

Michael Kochell

QA Assignee

Dylan Haussermann

Reporter

Michael Kochell

Epic Link

Fix versions

None

Mattermost Team

Integrations

Sprint

None

Labels

None

QA Testing Areas

Plugins

GitHub Issue

None

Components

None
Configure