Add OAuth 2.0 access-token authentication for on-premises NoSQL

[rajdeep714]

• Add OAuthAccessTokenProvider for exchanging an OCI IAM OAuth access token
  for a NoSQL login token through the HTTP proxy.
• Let applications supply and refresh access tokens through
  getAccessTokenInfo().
• Bind the handle to the KV-authenticated principal and reject login responses
  that omit the principal or switch identity without logout.
• Automatically refresh before the earlier of the OAuth access-token expiry
  and NoSQL login-token expiry.
• Retry a request once after an OAuth authentication failure and perform
  best-effort session cleanup when the provider closes.
• Configure the provider from NoSQLHandleConfig and preserve existing
  on-premises request-size and rate-limiting behavior.
• Integrate OAuth authorization with the existing on-premises examples through
  Common and the -useOAuth option.

Reviewed by: Ashutosh, Xiao, Yang

Tests:

• mvn -pl driver -Ptest-local
  -Dtest=OAuthAccessTokenProviderTest,AuthRetryTest test
• 11 tests passed.
• mvn -pl examples -am compile -DskipTests

Dependencies:

• Requires the corresponding HTTP proxy OAuth endpoints and KV OAuth support.

Files (Added / Modified / Deleted):

M README.md

• Documents how to run the existing on-premises examples using an OAuth access
  token without placing the bearer token on the command line.

M driver/pom.xml

• Adds OAuthAccessTokenProviderTest to the local driver test profile.

M driver/src/main/java/oracle/nosql/driver/http/Client.java

• Treats OAuthAccessTokenProvider as an on-premises provider for rate limiting
  and request-size enforcement. Flushes its cached login token and retries once
  after AuthenticationException, while preventing repeated retries.

M driver/src/main/java/oracle/nosql/driver/http/NoSQLHandleImpl.java

• Initializes OAuthAccessTokenProvider with the handle logger, normalized proxy
  endpoint, SSL context, and handshake timeout. Reuses the endpoint preparation
  logic with StoreAccessTokenProvider.

A driver/src/main/java/oracle/nosql/driver/kv/OAuthAccessTokenProvider.java

• Implements the OAuth access-token callback and HTTPS login exchange. Caches
  the returned NoSQL login token and authenticated principal, refreshes before
  the earlier token expiry, rejects principal changes, and performs best-effort
  cleanup of rejected or closed sessions.

M driver/src/test/java/oracle/nosql/driver/iam/AuthRetryTest.java

• Verifies that OAuth authentication failures cause one cache flush and one
  retry, with the second failure returned immediately.

A driver/src/test/java/oracle/nosql/driver/kv/OAuthAccessTokenProviderTest.java

• Covers login, request timeout propagation, automatic refresh, disabled
  renewal, login-token expiry, refresh failure, cache invalidation, principal
  validation, identity changes, missing principals, and logout on close.

M examples/src/main/java/Common.java

• Adds an OAuth mode shared by BasicTableExample, IndexExample, DeleteExample,
  and RateLimitingExample. It validates OAuth against the selected environment,
  rejects username/password combinations, and creates OAuthAccessTokenProvider
  from application-supplied token information.