dev: Update naive timestamps with UTC timezones

[akhercha]

Current Behavior

Currently, we store timestamps without any timezone information. This is a bad practice as it could lead to wrong interpretations at later stages.

Expected Behavior

• The timestamps in our databases should have TZ info
• The rust code should fetch timestamps as DateTime instead of NaiveDateTime
• E2E tests are added so we're sure everything works fine

[akhercha]

Changes reverted in

• pragma-monitoring: https://github.com/astraly-labs/pragma-monitoring/commit/fab52331b4f13bdab47fa16c0e6c9a2be5a5fd99
• pragma-node: https://github.com/astraly-labs/pragma-node/commit/f1171bd13d375faabae116f532a5ed58ae5f97e0

Those caused new entries to not be published & we had TimeSinceLastUpdateTooHigh alerts (causing WrongPrice alerts later).

Labels:
 - alertname = TimeSinceLastUpdateTooHigh
 - group = API
  - job = prometheus_monitoring
 - network = Testnet
 - pair = BTC/USD
 - severity = warning
Annotations:
 - description = The time since the last update for BTC/USD has exceeded 1800 seconds.
 - summary = Time since the last update is too high
Labels:
 - alertname = TimeSinceLastUpdateTooHigh
 - group = API
 - job = prometheus_monitoring
 - network = Testnet
 - pair = DAI/USD
 - severity = warning
Annotations:
 - description = The time since the last update for DAI/USD has exceeded 1800 seconds.
 - summary = Time since the last update is too high
Labels:
 - alertname = TimeSinceLastUpdateTooHigh
 - group = API
 - job = prometheus_monitoring
 - network = Testnet
 - pair = ETH/USD
 - severity = warning
Annotations:
 - description = The time since the last update for ETH/USD has exceeded 1800 seconds.
 - summary = Time since the last update is too high
Labels:
 - alertname = TimeSinceLastUpdateTooHigh
 - group = API
 - job = prometheus_monitoring
 - network = Testnet
 - pair = USDC/USD
 - severity = warning
Annotations:
 - description = The time since the last update for USDC/USD has exceeded 1800 seconds.
 - summary = Time since the last update is too high
Labels:
 - alertname = TimeSinceLastUpdateTooHigh
 - group = API
 - job = prometheus_monitoring
 - network = Testnet
 - pair = USDT/USD
 - severity = warning
Annotations:
 - description = The time since the last update for USDT/USD has exceeded 1800 seconds.
 - summary = Time since the last update is too high
Labels:
 - alertname = SourceDeviation
 - job = prometheus_monitoring
 - network = Testnet
 - pair = BTC/USD
 - severity = warning
 - source = BINANCE
 - type = future
Annotations:
 - description = The source deviation of BTC/USD from BINANCE has exceeded 2%.
 - summary = Source deviation is too high
Labels:
 - alertname = WrongPrice
 - job = prometheus_monitoring
 - network = Testnet
 - pair = BTC/USD
 - severity = warning
 - source = BINANCE
 - type = future
Annotations:
 - description = The price deviation of BTC/USD from BINANCE has exceeded 2.5%.
 - summary = Price deviation is too high

We reverted those changes and now everything works correctly.