Fix datetime utils to account for timezone interaction

[MatoPlus]

Ticket link

Closes #629 Closes #618 Closes #620 Closes #634 Closes #615

Implementation description

• 629 - Pending invites uses the createdAt field and we should respect the timezone for that backend fetched data

  • Created time util for getting local time/date for this pending invites user mangement modal

• 618 - Fixed various timezone issues, related to #620 fix

• 620 - Fixed dateInRange util, updated usage

• 634 - Make sure pending user invite modal filters for employee roles instead of admin roles for "admin" tab

• 615 - Add additional check to posting form shifts next handler to ensure that auto closing date has to be before the start date

• Updated various inappropriate usage dates from the backend. Displaying raw time when appropriate (eg: shift start/end time shouldn't be converted to local time)

Also, remove the unused VolunteerProfileShiftRow component.

Steps to test

• 629 - Invite users via user management, and go to invite modal, the date and time should be correct in ET timezone

• 618 - Volunteer cannot see postings with passed auto closing date in their shifts or postings tab

• 620 - Filter now respects that "This week/month" logic rather than doing a day diff count - use volunteer homepage to test out filter

• 634 - Invite admin and refresh page, that pending invite should appear in pending user invites modal

• 615 - Super admins can no longer create postings that with auto closing date after the posting start date, will get form error before submitting

What should reviewers focus on?

• Correctness

Checklist

• [x] My PR name is descriptive and in imperative tense
• [x] My commit messages are descriptive and in imperative tense. My commits are atomic and trivial commits are squashed or fixup'd into non-trivial commits
• [x] I have run the appropriate linter(s)
• [x] I have requested a review from the PL, as well as other devs who have background knowledge on this PR or who will be building on top of this PR

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[MatoPlus]

merged to unblock other tickets. Feel free to lmk for any requests