feat: ParseObject's now conform to Identifiable

[cbaker6]

New Pull Request Checklist

• I am not disclosing a vulnerability.
• I am creating this PR in reference to an issue.

Issue Description

Support Identifiable natively for ParseObject's and remove support for older OS's, iOS 12, tvOS 12, watchOS 5, and macOS 10.13/14.

Adds configuration option to delete Keychain on app first run. This option is disabled by default and should only be enabled after the following in order to avoid users having to re-login:

1. Update to Swift SDK 2.0.0
2. Run/open the Swift SDK based app at least 1 time
3. Then enable the setting:

let newConfiguration = ParseConfiguration(applicationId: "applicationId",
                                                      serverURL: server,
                                                      deleteKeychainIfNeeded: false)
ParseSwift.initialize(configuration: newConfiguration)

Related issue: #255, #246

Approach

Bump minimum version numbers and remove code checks for unsupported version types.

TODOs before merging

• Remove all references to old OS availability
• Remove LocallyIdentifiable protocol and replace with Identifiable for ParseFile
• Add entry to changelog
• Add changes to documentation (guides, repository pages, in-code descriptions)

[codecov]

Codecov Report

Merging #254 (cf27146) into main (85366e6) will increase coverage by 0.07%.
The diff coverage is 81.39%.

@@            Coverage Diff             @@
##             main     #254      +/-   ##
==========================================
+ Coverage   76.67%   76.74%   +0.07%     
==========================================
  Files          99       98       -1     
  Lines       10382    10403      +21     
==========================================
+ Hits         7960     7984      +24     
+ Misses       2422     2419       -3     

Impacted Files	Coverage Δ
...tion/3rd Party/ParseApple/ParseApple+combine.swift	100.00% <ø> (ø)
...rd Party/ParseFacebook/ParseFacebook+combine.swift	100.00% <ø> (ø)
...cation/3rd Party/ParseLDAP/ParseLDAP+combine.swift	100.00% <ø> (ø)
.../3rd Party/ParseTwitter/ParseTwitter+combine.swift	100.00% <ø> (ø)
...thentication/Internal/ParseAnonymous+combine.swift	100.00% <ø> (ø)
...cation/Protocols/ParseAuthentication+combine.swift	85.71% <ø> (ø)
...Authentication/Protocols/ParseAuthentication.swift	70.98% <ø> (ø)
Sources/ParseSwift/LiveQuery/LiveQuerySocket.swift	59.80% <ø> (ø)
.../ParseSwift/LiveQuery/ParseLiveQuery+combine.swift	72.72% <ø> (ø)
Sources/ParseSwift/LiveQuery/ParseLiveQuery.swift	73.08% <ø> (ø)
... and 25 more

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