refactor(ble): minor BLE library cleanup

[Kolcha]

Checklist

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Description of Change

minor BLE library cleanup:

• made many getters const (as it supposed to be)
• pass string by reference in modified classes
• other random code cleanup / fixes

Test Scenarios

I have tested my Pull Request on Arduino-esp32 core v3.3.0 with ESP32. Successful build is enough to confirm that everything is ok.

Related links

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Test Results

76 files 76 suites 14m 28s ⏱️
38 tests 38 ✅ 0 💤 0 ❌
241 runs 241 ✅ 0 💤 0 ❌

Results for commit 3c31d67.

♻️ This comment has been updated with latest results.

[github-actions]

Memory usage test (comparing PR against master branch)

The table below shows the summary of memory usage change (decrease - increase) in bytes and percentage for each target.

Memory	FLASH [bytes]		FLASH [%]		RAM [bytes]		RAM [%]
Target	DEC	INC	DEC	INC	DEC	INC	DEC	INC
ESP32C5	💚 -38	⚠️ +2	0.00	0.00	0	0	0.00	0.00
ESP32S3	💚 -12	⚠️ +24	0.00	0.00	0	0	0.00	0.00
ESP32C3	💚 -38	⚠️ +2	💚 -0.01	0.00	0	0	0.00	0.00
ESP32C6	💚 -38	⚠️ +2	💚 -0.01	0.00	0	0	0.00	0.00
ESP32H2	💚 -38	⚠️ +2	💚 -0.01	0.00	0	0	0.00	0.00
ESP32	💚 -16	⚠️ +28	0.00	0.00	0	0	0.00	0.00

Click to expand the detailed deltas report [usage change in BYTES]

Target	ESP32C5		ESP32S3		ESP32C3		ESP32C6		ESP32H2		ESP32
Example	FLASH	RAM	FLASH	RAM	FLASH	RAM	FLASH	RAM	FLASH	RAM	FLASH	RAM
libraries/BLE/examples/Beacon_Scanner	💚 -38	0	💚 -12	0	💚 -38	0	💚 -38	0	💚 -38	0	💚 -16	0
libraries/BLE/examples/Client	⚠️ +2	0	⚠️ +24	0	⚠️ +2	0	⚠️ +2	0	⚠️ +2	0	⚠️ +24	0
libraries/BLE/examples/Client_secure_static_passkey	⚠️ +2	0	⚠️ +24	0	⚠️ +2	0	⚠️ +2	0	⚠️ +2	0	⚠️ +24	0
libraries/BLE/examples/EddystoneTLM_Beacon	⚠️ +2	0	⚠️ +24	0	⚠️ +2	0	⚠️ +2	0	⚠️ +2	0	⚠️ +24	0
libraries/BLE/examples/EddystoneURL_Beacon	⚠️ +2	0	⚠️ +24	0	⚠️ +2	0	⚠️ +2	0	⚠️ +2	0	⚠️ +24	0
libraries/BLE/examples/Notify	⚠️ +2	0	⚠️ +24	0	⚠️ +2	0	⚠️ +2	0	⚠️ +2	0	⚠️ +24	0
libraries/BLE/examples/Scan	⚠️ +2	0	⚠️ +24	0	⚠️ +2	0	⚠️ +2	0	⚠️ +2	0	⚠️ +24	0
libraries/BLE/examples/Server	⚠️ +2	0	⚠️ +24	0	⚠️ +2	0	⚠️ +2	0	⚠️ +2	0	⚠️ +28	0
libraries/BLE/examples/Server_multiconnect	⚠️ +2	0	⚠️ +24	0	⚠️ +2	0	⚠️ +2	0	⚠️ +2	0	⚠️ +24	0
libraries/BLE/examples/Server_secure_static_passkey	⚠️ +2	0	⚠️ +24	0	⚠️ +2	0	⚠️ +2	0	⚠️ +2	0	⚠️ +24	0
libraries/BLE/examples/UART	⚠️ +2	0	⚠️ +24	0	⚠️ +2	0	⚠️ +2	0	⚠️ +2	0	⚠️ +24	0
libraries/BLE/examples/Write	⚠️ +2	0	⚠️ +24	0	⚠️ +2	0	⚠️ +2	0	⚠️ +2	0	⚠️ +24	0
libraries/BLE/examples/iBeacon	⚠️ +2	0	⚠️ +24	0	⚠️ +2	0	⚠️ +2	0	⚠️ +2	0	⚠️ +24	0

[lucasssvaz]

Could you rebase your PR with the latest BLE changes ?

[Kolcha]

rebased

[SuGlider]

LGTM. Thanks @Kolcha for the contribution!