[WithSecure Elements] Add missing fields and documentation improvements

[fspms]

Summary

This PR updates the WithSecure Elements integration to version 0.2.0 by adding missing fields from the API specifications and improving documentation.

Changes

Field Additions

• Security Events: Added 60+ missing fields from the API specifications covering all event types:
  • EDR/XDR events: readableIncidentId, mergedTo
  • File Scanning events: systemWide, readOnly, rebootRequiredToDelete, availableActions, recommendedAction, containerSize, containerMailbox, subItem, accessOperation, accessFlags, accessorHash, accessorPath
  • Application Control events: targetFileVersion, targetPrevalence, targetProductName, targetProductVersion, targetSignatureSignerName, targetVersionCompanyName, errorMessage
  • Server Share Protection/Rollback events: items, backupFolder, isQuarantineAllowed, processOperations, registryOperations
  • Web Traffic Scanning events: contentType, websiteUrl, computerName
  • Firewall events: ruleGroupName, layerName, ruleDirection, ipProtocol
  • DeepGuard events: rarity, exploit, commandLine
  • Device Control events: devicePath, deviceId, deviceName, initiator
  • Integrity Checker events: processId
  • Tamper Protection events: actionType, initiator_certificate_hash, initiator_signer_name, ipAddress, requestType
  • XFence events: operation, processHash, processPath, processTeamId
  • Collaboration Protection (ECP) events: serviceId, inboxRuleName, prevalenceScore, filename, and all ECP-specific fields
  • XM (Exposure Management) events: recommendationDetails, recommendationId, recommendationName, recommendationStatus, remediationEffort, remediationEffortString, remediationImpact, topAssets, totalAssets, topFindings, totalFindings
  • AMSI events: appName, contentName
  • Connector events: daysFromLastUpdate
• Root level fields: Added server_timestamp and xmRecommendationKey
• Device fields: Added winsAddress, winsName, clientType
• Incidents: Added description field

Configuration Updates

• Added ECP (Collaboration Protection) and XM (Exposure Management) to default engine groups configuration
• All four engine groups (EPP, EDR, ECP, XM) are now enabled by default

Documentation Improvements

• Updated README with comprehensive field listing (removed generic ECS fields, kept only WithSecure-specific fields)
• Added detailed setup instructions with screenshots for API client creation
• Improved field descriptions with event type context

Version Update

• Updated package version from 0.1.0 to 0.2.0
• Updated changelog with all changes following Elastic conventions