issue 5747 refactor content scripts for Thunderbird

[tomholub]

This PR attempts to clean up content script code and make it easier to add another environment (like another webmail, or Thunderbird)

Further, test logging output was cleaned up a bit, and debug html files are uploaded to artifacts again.

close #5747 issue #5396

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Tests (delete all except exactly one):

• Does not need tests (refactor only, docs or internal changes)

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To be filled by reviewers

I have reviewed that this PR... (tick whichever items you personally focused on during this review):

• [x] addresses the issue it closes (if any)
• [x] code is readable and understandable
• [x] is accompanied with tests, or tests are not needed
• [x] is free of vulnerabilities
• [x] is documented clearly and usefully, or doesn't need documentation

[tomholub]

After this PR, Thunderbird could be added like so:

Catch.try(async () => {
+if(this is thunderbird) {
+  await new ThunderbirdWebmailStartup().asyncConstructor();
+} else {
  await new GmailWebmailStartup().asyncConstructor();
+}
})();

// content_scripts/webmail/thunderbird/thunderbird-webmail-startup.ts

export class ThunderbirdWebmailStartup {
  private replacePgpElsInterval: number;
  private replacer: GmailElementReplacer;

  public asyncConstructor = async () => {
    await contentScriptSetupIfVacant({
      name: 'thunderbird',
      variant: undefined,
      getUserAccountEmail: () => undefined, // todo, but can start with undefined
      getUserFullName: () => undefined // todo, but can start with undefined
      getReplacer: () => new ThunderbirdElementReplacer(), // todo - add this class empty, methods do nothing
      start: this.start
    });
  }

    private start = async (
      acctEmail: string,
      clientConfiguration: ClientConfiguration,
      injector: Injector,
      notifications: Notifications,
      factory: XssSafeFactory,
      relayManager: RelayManager
    ) => {
      // injector.btns(); // todo in another issue - add compose button
      this.replacer.runIntervalFunctionsPeriodically();
      await notifications.showInitial(acctEmail);
      await notifications.show('FlowCrypt Thunderbird support is still in early development, and not expected to function properly yet. Support will be gradually added in upcoming versions.');
    }
  };
};