Add WaveTrend Oscillator indicator

[AlexCatarino]

Description

Implements WaveTrendOscillator (a BarIndicator consuming IBaseDataBar) per the linked issue. Adds the indicator class, the WTO helper on QCAlgorithm.Indicators.cs, unit tests inheriting CommonIndicatorTests<IBaseDataBar>, and the reference CSV spy_wto.csv under Tests/TestData/.

The indicator produces two lines:

• WT1 (primary Current.Value) — EMA(ci, averagePeriod)
• WT2 (exposed via the Signal sub-indicator) — SMA(WT1, signalPeriod)

where

hlc3 = (High + Low + Close) / 3
esa  = EMA(hlc3, channelPeriod)
d    = EMA(|esa - hlc3|, channelPeriod)
ci   = (hlc3 - esa) / (0.015 * d)

IsReady tracks Signal.IsReady; WarmUpPeriod = 2 * channelPeriod + averagePeriod + signalPeriod - 3 (42 with the (10, 21, 4) defaults from the original TradingView script).

Related Issue

Closes #6411

Motivation and Context

Requested via #6411 to bring the WaveTrend Oscillator (popularized by LazyBear on TradingView) to LEAN's indicator library. It's a widely used momentum oscillator for spotting overbought/oversold conditions and WT1/WT2 crossovers; users following TradingView-style strategies currently have no built-in equivalent.

Requires Documentation Change

Yes — add the following entry to Documentation/Resources/indicators/IndicatorImageGenerator.py (in the indicators dict):

'Wave-Trend-Oscillator': IndicatorInfo(
    WaveTrendOscillator(10, 21, 4),
    'WaveTrendOscillator(10, 21, 4)',
    'WTO(_symbol, 10, 21, 4)',
    'self.wto(self._symbol, 10, 21, 4)'
),

How Has This Been Tested?

• dotnet build QuantConnect.Lean.sln
• dotnet test Tests/QuantConnect.Tests.csproj --filter "FullyQualifiedName~WaveTrendOscillatorTests" — 16/16 passing in ~6 s.
• Reference TCI column in spy_wto.csv was generated with TA-Lib (talib.EMA, talib.SMA) from the public SPY daily data shipped in Data/equity/usa/daily/spy.zip, matching the generator from the issue comment thread. CommonIndicatorTests.ComparesAgainstExternalData verifies LEAN's WT1 matches to within 1e-3.

Types of changes

• New feature (non-breaking change which adds functionality)

Checklist:

• My code follows the code style of this project.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.
• My branch follows the naming convention feature-<N>-<description>.